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$43+ Cheap flights from Seattle (SEA) to Boulder, CO

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 5/18. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — DEN
Mar 21 — Mar 281
Sat 3/21
Sat 3/28
1 adult, Economy
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Cheapflights Tip: The best prices from Seattle/Tacoma Intl to Boulder are usually found in January or September, booked 69 days in advance, depart on a Friday or Saturday and return on a Thursday

Cheap flight deals from Seattle to Boulder

Cheapest flights from Seattle to Boulder
Explore the most affordable flight options available from Seattle to Boulder. Find the lowest fares from popular airlines and budget airlines, with prices last updated on February 19, 2026.

This Cheapflightsfares deal was found by Cheapflights users on 2/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 5/46:57 pm
SEA
-
DEN
Nonstop2h 52m
Frontier
Fri 5/812:51 pm
DEN
-
SEA
Nonstop3h 14m
Frontier
Deal found 2/18$72
This Orbitz deal was found by Cheapflights users on 2/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Orbitz is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/167:12 pm
SEA
-
DEN
Nonstop2h 47m
Frontier
Sun 4/197:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 2/17$73
This Kiwi.com deal was found by Cheapflights users on 2/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 4/234:20 pm
SEA
-
DEN
Nonstop2h 51m
Frontier
Mon 4/2712:51 pm
DEN
-
SEA
Nonstop3h 14m
Frontier
Deal found 2/17$80
This Orbitz deal was found by Cheapflights users on 2/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Orbitz is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 4/178:11 pm
SEA
-
DEN
Nonstop2h 45m
Multiple Airlines
Tue 4/287:15 am
DEN
-
SEA
Nonstop3h 12m
Multiple Airlines
Deal found 2/15$82
This Orbitz deal was found by Cheapflights users on 2/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Orbitz is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/156:57 pm
SEA
-
DEN
Nonstop2h 52m
Multiple Airlines
Tue 4/217:00 am
DEN
-
SEA
Nonstop3h 10m
Multiple Airlines
Deal found 2/17$85
This Kiwi.com deal was found by Cheapflights users on 2/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/1510:42 am
SEA
-
DEN
1 stop8h 07m
Frontier
Tue 4/217:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 2/18$86
This Expedia deal was found by Cheapflights users on 2/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/18:05 pm
SEA
-
DEN
Nonstop2h 54m
Multiple Airlines
Mon 5/412:51 pm
DEN
-
SEA
Nonstop3h 14m
Multiple Airlines
Deal found 2/18$87
This Cheapflightsfares deal was found by Cheapflights users on 2/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 5/16:57 pm
SEA
-
DEN
Nonstop2h 52m
Frontier
Sun 5/37:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 2/18$88
This Kiwi.com deal was found by Cheapflights users on 2/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 4/118:11 pm
SEA
-
DEN
Nonstop2h 45m
Multiple Airlines
Tue 4/147:15 am
DEN
-
SEA
Nonstop3h 12m
Multiple Airlines
Deal found 2/17$91
This Kiwi.com deal was found by Cheapflights users on 2/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/88:11 pm
SEA
-
DEN
Nonstop2h 45m
Multiple Airlines
Wed 4/157:15 am
DEN
-
SEA
Nonstop3h 12m
Multiple Airlines
Deal found 2/17$92
This Frontier deal was found by Cheapflights users on 2/17. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 4/226:57 pm
SEA
-
DEN
Nonstop2h 52m
Frontier
Wed 4/297:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 2/17$93
This Kiwi.com deal was found by Cheapflights users on 2/18. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 3/1212:24 pm
SEA
-
DEN
Nonstop2h 51m
Frontier
Mon 3/166:11 am
DEN
-
SEA
1 stop15h 10m
Frontier
Deal found 2/18$95

Find flight deals from Seattle to Boulder

Keep the following information in mind while searching for Seattle to Boulder flight deals. Data was last updated February 19, 2026.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$72
(Cheapflightsfares)

One-way from

$43
(Kiwi.com)

Popular in

June

Cheapest in

January

Average price

$205
Provider with most accurate pricing for Seattle/Tacoma Intl-Denver Intl flight deals.
Search Deals
Provider most trusted by Cheapflights users for Seattle/Tacoma Intl-Denver Intl flights.
Search Deals
From Seattle/Tacoma Intl to Boulder
Search Deals
One-way flight from Seattle/Tacoma Intl to Boulder
Search Deals
Highest demand for flights based on searches. 8% potential increase in price ($19 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 1% potential price decrease ($3 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in February 2026
Search Deals

Cheapflights Fare Finder

 
Customize your flight search to find flights from Seattle to Boulder that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated February 19, 2026.
Use the filters below to find and compare flights from Seattle to Boulder that are best for you.

Fly from

Seattle

Fly to

Boulder

Route

Depart

Return

Price

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Mon 4/6

7:46 pm-11:32 pm

Nonstop2h 46m

Denver Intl

Thu 4/9

6:30 am-8:38 am

Nonstop3h 08m

$97

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sun 4/12

7:05 pm-10:56 pm

Nonstop2h 51m

Denver Intl

Sun 4/19

8:35 pm-10:33 pm

Nonstop2h 58m

$97

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sun 4/12

7:46 pm-11:32 pm

Nonstop2h 46m

Denver Intl

Thu 4/23

6:55 am-9:01 am

Nonstop3h 06m

$97

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Thu 4/16

4:36 pm-10:29 pm

1 stop4h 53m

Denver Intl

Thu 4/23

7:45 pm-10:05 pm

Nonstop3h 20m

$107

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sat 4/4

7:46 pm-11:32 pm

Nonstop2h 46m

Denver Intl

Sun 4/5

8:00 am-2:54 pm

1 stop7h 54m

$107

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Thu 4/30

8:35 am-12:17 pm

Nonstop2h 42m

Denver Intl

Mon 5/4

6:27 pm-11:59 pm

1 stop6h 32m

$107

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Thu 4/16

4:36 pm-10:29 pm

1 stop4h 53m

Denver Intl

Tue 4/21

6:55 am-9:01 am

Nonstop3h 06m

$107

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Thu 4/16

4:36 pm-10:29 pm

1 stop4h 53m

Denver Intl

Sat 4/18

6:55 am-9:01 am

Nonstop3h 06m

$107

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Thu 3/12

7:45 pm-11:29 pm

Nonstop2h 44m

Denver Intl

Sat 3/14

4:00 pm-10:01 pm

1 stop7h 01m

$107

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sat 5/9

5:30 am-11:53 am

1 stop5h 23m

Denver Intl

Mon 5/11

3:48 pm-10:01 pm

1 stop7h 13m

$117

Flights are sorted by cheapest round-trip flights first.

Deals found on 2/18

Showing 1-10 of 22 results
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Best time to book a flight from Seattle to Boulder

Have a flexible travel schedule? Discover the best time to fly to Boulder from Seattle with our price prediction graph.
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

Everything you need to know about your flight from Seattle to Boulder

How far ahead should I book a flight from Seattle to Boulder?

Use this chart to determine the optimal time to book a round-trip flight from Seattle to Boulder. Price data was last updated on February 18, 2026.

Booking 69 days in advance of your planned departure date is, on average, the best time to get cheap flights from Seattle to Boulder. The general trend is that the closer you book to the departure date, the more expensive your flight will be.

What is the cheapest month to book a flight from Seattle to Boulder?

Currently, January is the cheapest month in which you can book a flight from Seattle to Boulder (average of $53). Flying from Seattle to Boulder in July is currently the most expensive (average of $110). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

What is the cheapest time of day to fly from SEA to BD9?

Find hourly flight availability from Seattle to Boulder. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated February 19, 2026.

Unlike in the morning, when flights are generally more expensive, you can save up to 21% on flights from Seattle to Boulder by exploring options for tickets in the evening.

What is the cheapest day to fly from Seattle to Boulder?

Use this chart to determine the cheapest time to fly round-trip from Seattle to Boulder. Price data was last updated on February 17, 2026.

Travelers seeking maximum savings on their Seattle to Boulder flight should consider departing on Wednesday evenings when fares are most often at their lowest. Monday mornings flights should be avoided if possible as fares are typically the most expensive at this time.

Weekly flight availability from Seattle to Boulder

Explore weekly flight availability from Seattle to Boulder. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated February 19, 2026.

The most flights from SEA to BD9 are scheduled on a Monday (42 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (23 on average).

Reviews of airlines servicing Boulder

Get insights into the airlines that provide service to Boulder. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Boulder. Reviews last updated February 19, 2026.
See what other customers who have flown with Alaska Airlines, Southwest, and Delta from Seattle to Boulder have to say. You can also see how each airline compares in terms of entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
8.0
Very good
11,904 reviews

Comfort

7.8

Crew

8.5

Boarding

8.1

Entertainment

7.0

Food

7.1

Overall

8.0

Reviews

1 / 20
4.0
Okay

Anonymous,Dec 2025

SEA - MSY

I really got a lesson in upgrades. I let my seat get chosen . Both times a middle seat...on purpose ...even when we were not full. That's petty I sat behind the first class . They got more than 1 drink ...and a snack . .and the staff actually talked to them...behind a see thru shawl/sheet in the aisle....... You could see over the seats just fine and you could hear the voices just fine. But the sheet let You KNOW. Your not welcome here. For a moment I regretted not spending 300 dollars per seat so I could see a smile and eat a sandwhich and enjoy my seat . The married couple drank champain and laughed and flirted with each other. It looked so happy and care free MONEY really does buy happiness ..the hateful glares and sighs from my seat mates brought me back to reality I wasn't rich and I still had 2 hours left in this middle seat.
Alaska Airlines
8.0
Very good
11,904 reviews
Alaska Airlines
8.0
Very good
11,904 reviews

Comfort

7.8

Crew

8.5

Boarding

8.1

Entertainment

7.0

Food

7.1

Overall

8.0

Reviews

1 / 20
4.0
Okay

Anonymous,Dec 2025

SEA - MSY

I really got a lesson in upgrades. I let my seat get chosen . Both times a middle seat...on purpose ...even when we were not full. That's petty I sat behind the first class . They got more than 1 drink ...and a snack . .and the staff actually talked to them...behind a see thru shawl/sheet in the aisle....... You could see over the seats just fine and you could hear the voices just fine. But the sheet let You KNOW. Your not welcome here. For a moment I regretted not spending 300 dollars per seat so I could see a smile and eat a sandwhich and enjoy my seat . The married couple drank champain and laughed and flirted with each other. It looked so happy and care free MONEY really does buy happiness ..the hateful glares and sighs from my seat mates brought me back to reality I wasn't rich and I still had 2 hours left in this middle seat.
Southwest
8.0
Very good
4,295 reviews
Alaska Airlines
8.0
Very good
11,904 reviews

Comfort

7.8

Crew

8.5

Boarding

8.1

Entertainment

7.0

Food

7.1

Overall

8.0

Reviews

1 / 20
4.0
Okay

Anonymous,Dec 2025

SEA - MSY

I really got a lesson in upgrades. I let my seat get chosen . Both times a middle seat...on purpose ...even when we were not full. That's petty I sat behind the first class . They got more than 1 drink ...and a snack . .and the staff actually talked to them...behind a see thru shawl/sheet in the aisle....... You could see over the seats just fine and you could hear the voices just fine. But the sheet let You KNOW. Your not welcome here. For a moment I regretted not spending 300 dollars per seat so I could see a smile and eat a sandwhich and enjoy my seat . The married couple drank champain and laughed and flirted with each other. It looked so happy and care free MONEY really does buy happiness ..the hateful glares and sighs from my seat mates brought me back to reality I wasn't rich and I still had 2 hours left in this middle seat.
Delta
7.9
Good
8,213 reviews
Alaska Airlines
8.0
Very good
11,904 reviews

Comfort

7.8

Crew

8.5

Boarding

8.1

Entertainment

7.0

Food

7.1

Overall

8.0

Reviews

1 / 20
4.0
Okay

Anonymous,Dec 2025

SEA - MSY

I really got a lesson in upgrades. I let my seat get chosen . Both times a middle seat...on purpose ...even when we were not full. That's petty I sat behind the first class . They got more than 1 drink ...and a snack . .and the staff actually talked to them...behind a see thru shawl/sheet in the aisle....... You could see over the seats just fine and you could hear the voices just fine. But the sheet let You KNOW. Your not welcome here. For a moment I regretted not spending 300 dollars per seat so I could see a smile and eat a sandwhich and enjoy my seat . The married couple drank champain and laughed and flirted with each other. It looked so happy and care free MONEY really does buy happiness ..the hateful glares and sighs from my seat mates brought me back to reality I wasn't rich and I still had 2 hours left in this middle seat.
United Airlines
7.4
Good
9,322 reviews
Alaska Airlines
8.0
Very good
11,904 reviews

Comfort

7.8

Crew

8.5

Boarding

8.1

Entertainment

7.0

Food

7.1

Overall

8.0

Reviews

1 / 20
4.0
Okay

Anonymous,Dec 2025

SEA - MSY

I really got a lesson in upgrades. I let my seat get chosen . Both times a middle seat...on purpose ...even when we were not full. That's petty I sat behind the first class . They got more than 1 drink ...and a snack . .and the staff actually talked to them...behind a see thru shawl/sheet in the aisle....... You could see over the seats just fine and you could hear the voices just fine. But the sheet let You KNOW. Your not welcome here. For a moment I regretted not spending 300 dollars per seat so I could see a smile and eat a sandwhich and enjoy my seat . The married couple drank champain and laughed and flirted with each other. It looked so happy and care free MONEY really does buy happiness ..the hateful glares and sighs from my seat mates brought me back to reality I wasn't rich and I still had 2 hours left in this middle seat.
Frontier
5.7
Fair
3,048 reviews
Alaska Airlines
8.0
Very good
11,904 reviews

Comfort

7.8

Crew

8.5

Boarding

8.1

Entertainment

7.0

Food

7.1

Overall

8.0

Reviews

1 / 20
4.0
Okay

Anonymous,Dec 2025

SEA - MSY

I really got a lesson in upgrades. I let my seat get chosen . Both times a middle seat...on purpose ...even when we were not full. That's petty I sat behind the first class . They got more than 1 drink ...and a snack . .and the staff actually talked to them...behind a see thru shawl/sheet in the aisle....... You could see over the seats just fine and you could hear the voices just fine. But the sheet let You KNOW. Your not welcome here. For a moment I regretted not spending 300 dollars per seat so I could see a smile and eat a sandwhich and enjoy my seat . The married couple drank champain and laughed and flirted with each other. It looked so happy and care free MONEY really does buy happiness ..the hateful glares and sighs from my seat mates brought me back to reality I wasn't rich and I still had 2 hours left in this middle seat.

Related info for your journey

Find useful and relevant information for your journey from Seattle to Boulder. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • What airport do you fly from for flights from Seattle to Boulder?

    Seattle/Tacoma Intl (SEA) is the airport you will fly out of if you book a flight from Seattle to Boulder. You should not have trouble finding flights to Boulder from Seattle/Tacoma Intl; the airport handles an average of 30 outbound flights to Boulder per day. You should also have plenty of airline options to choose from since 6 airlines have flights from the Seattle airport to Boulder. It is only a 11.4 mi journey to Seattle/Tacoma Intl (SEA) from Seattle’s city center.

  • How popular is this Seattle to Boulder flight route?

    Flights from Seattle/Tacoma Intl to Boulder have been viewed 280 times in the past calendar month.

  • How long is the flight from Seattle to Boulder?

    There are many flights that can get you from Seattle to Boulder in 2h 46m. Fly via Delta or United Airlines to get the fastest option. Airlines will cover a distance of 1022 mi. Generally, flights for this route are nonstop.

  • What are the cheapest airlines to fly from Seattle to Boulder one-way?

    To fly one-way, consider booking your trip with Frontier, which is currently one of the cheapest options available, starting at $29. United Airlines flights start at $59 while deals on Delta start at $68 one-way.

  • What are the most reliable airlines from Seattle to Boulder?

    Before booking your flight to Boulder from Seattle, check out the most reliable airlines to get you to your destination on time: Aeromexico (93%), Southwest (92%), SkyWest Airlines( 92%).

  • What are the cheapest flights from Seattle to Boulder?

    Looking for the cheapest flight from Seattle to Boulder? While on average our users pay $711, our data indicates the cheapest price to be $67. The most popular route (Seattle/Tacoma Intl - Denver Intl), is priced around $46.

  • Can I find deals for flights from Seattle to Boulder that include hotel bookings?

    Yes. In addition to deals on Seattle to Boulder flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Seattle to Boulder?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Seattle to Boulder.

  • Can I find deals for business class flights from Seattle to Boulder?

    Yes. Cheapflights offers flight deals from Seattle to Boulder by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • What is the cheapest month to book a flight from Seattle to Boulder?

    Currently, January is the cheapest month in which you can book a flight from Seattle to Boulder (average of $53). Flying from Seattle to Boulder in July is currently the most expensive (average of $110). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

Browse thousands of different options on Cheapflights for your next trip

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Top 6 airlines flying from Seattle to Boulder

Discover the top 6 airlines that operate flights from Seattle to Boulder. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated February 19, 2026.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$57Average$164FlexibilityNo cancel feeOn-time62%
Hawaiian AirlinesCheapest$78Average$215FlexibilityNo cancel feeOn-time85%
DeltaCheapest$98Average$238FlexibilityNo cancel feeOn-timeN/A
Alaska AirlinesCheapest$117Average$280FlexibilityNo cancel feeOn-time75%
SouthwestCheapest$127Average$313FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$131Average$389FlexibilityNo cancel feeOn-time69%

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