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$79+ 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 9/10. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — DEN
Aug 16 — Aug 231
Sat 8/16
Sat 8/23
1 adult, Economy
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Cheapflights Tip: The best prices from Seattle/Tacoma Intl to Boulder are usually found in October or September, booked 77 days in advance, depart on a Saturday or Thursday and return on a Thursday

Cheap flight deals from Seattle to Boulder

Keep the following information in mind while searching for Seattle to Boulder flight deals. Data was last updated August 11, 2025.

Round-trip from

$112
(Cheapflightsfares)

One-way from

$79
(Southwest)

Popular in

December

Cheapest in

October

Average price

$215
From Seattle/Tacoma Intl to Boulder
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One-way flight from Seattle/Tacoma Intl to Boulder
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High demand for flights, 0% potential price rise
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Cheapest flight prices on average. 2% potential price decrease ($5 potential savings vs. average RT price).
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Average for round-trip flights in August 2025
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Find 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 August 11, 2025.

This Cheapflightsfares deal was found by Cheapflights users on 8/11. 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.
Wed 9/36:41 amSEA - DEN
Nonstop2h 49mFrontier
Tue 9/98:55 pmDEN - SEA
Nonstop3h 04mFrontier
Deal found 8/11$112
This Frontier deal was found by Cheapflights users on 8/11. 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.
Sat 9/67:00 amSEA - DEN
Nonstop2h 53mFrontier
Tue 9/98:55 pmDEN - SEA
Nonstop3h 04mFrontier
Deal found 8/11$114
This Cheapflightsfares deal was found by Cheapflights users on 8/11. 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 9/56:12 amSEA - DEN
Nonstop2h 56mFrontier
Mon 9/810:29 pmDEN - SEA
Nonstop3h 01mFrontier
Deal found 8/11$115
This Cheapflightsfares deal was found by Cheapflights users on 8/11. 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 9/266:12 amSEA - DEN
Nonstop2h 56mFrontier
Sun 9/2810:29 pmDEN - SEA
Nonstop3h 01mFrontier
Deal found 8/11$116
This Cheapflightsfares deal was found by Cheapflights users on 8/9. 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.
Thu 8/286:17 amSEA - DEN
Nonstop2h 49mFrontier
Mon 9/17:30 amDEN - SEA
Nonstop3h 04mFrontier
Deal found 8/9$117
This Frontier deal was found by Cheapflights users on 8/8. 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.
Sun 10/268:43 pmSEA - DEN
Nonstop2h 52mFrontier
Sun 11/1610:29 pmDEN - SEA
Nonstop3h 02mFrontier
Deal found 8/8$118
This Frontier deal was found by Cheapflights users on 8/8. 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.
Mon 10/278:43 pmSEA - DEN
Nonstop2h 52mFrontier
Mon 11/1710:29 pmDEN - SEA
Nonstop3h 02mFrontier
Deal found 8/8$119
This Frontier deal was found by Cheapflights users on 8/10. 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.
Fri 9/126:12 amSEA - DEN
Nonstop2h 56mFrontier
Fri 9/1210:29 pmDEN - SEA
Nonstop3h 01mFrontier
Deal found 8/10$120
This Cheapflightsfares deal was found by Cheapflights users on 8/10. 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.
Sat 8/3012:40 pmSEA - DEN
Nonstop2h 54mFrontier
Sun 8/317:30 amDEN - SEA
Nonstop3h 04mFrontier
Deal found 8/10$121
This Frontier deal was found by Cheapflights users on 8/10. 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.
Fri 11/146:00 amSEA - DEN
Nonstop2h 51mFrontier
Mon 11/1710:29 pmDEN - SEA
Nonstop3h 02mFrontier
Deal found 8/10$122
This Frontier deal was found by Cheapflights users on 8/10. 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.
Fri 9/266:12 amSEA - DEN
Nonstop2h 56mFrontier
Wed 10/18:55 pmDEN - SEA
Nonstop3h 04mFrontier
Deal found 8/10$123
This Frontier deal was found by Cheapflights users on 8/10. 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.
Thu 10/26:12 amSEA - DEN
Nonstop2h 56mFrontier
Sun 10/510:29 pmDEN - SEA
Nonstop3h 01mFrontier
Deal found 8/10$124

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 August 11, 2025.
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

Wed 9/3

6:41 am-10:30 am

Nonstop2h 49m

Denver Intl

Tue 9/9

8:55 pm-10:59 pm

Nonstop3h 04m

$112

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sat 9/6

7:00 am-10:53 am

Nonstop2h 53m

Denver Intl

Tue 9/9

8:55 pm-10:59 pm

Nonstop3h 04m

$114

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Fri 9/5

6:12 am-10:08 am

Nonstop2h 56m

Denver Intl

Mon 9/8

10:29 pm-12:30 am

Nonstop3h 01m

$115

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Fri 9/26

6:12 am-10:08 am

Nonstop2h 56m

Denver Intl

Sun 9/28

10:29 pm-12:30 am

Nonstop3h 01m

$116

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Thu 8/28

6:17 am-10:06 am

Nonstop2h 49m

Denver Intl

Mon 9/1

7:30 am-9:34 am

Nonstop3h 04m

$117

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sun 10/26

8:43 pm-12:35 am

Nonstop2h 52m

Denver Intl

Sun 11/16

10:29 pm-12:31 am

Nonstop3h 02m

$118

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Mon 10/27

8:43 pm-12:35 am

Nonstop2h 52m

Denver Intl

Mon 11/17

10:29 pm-12:31 am

Nonstop3h 02m

$119

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Fri 9/12

6:12 am-10:08 am

Nonstop2h 56m

Denver Intl

Fri 9/12

10:29 pm-12:30 am

Nonstop3h 01m

$120

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sat 8/30

12:40 pm-4:34 pm

Nonstop2h 54m

Denver Intl

Sun 8/31

7:30 am-9:34 am

Nonstop3h 04m

$121

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Fri 10/10

6:00 am-9:51 am

Nonstop2h 51m

Denver Intl

Sun 10/12

10:29 pm-12:31 am

Nonstop3h 02m

$122

Flights are sorted by cheapest round-trip flights first.

Deals found on 8/11

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 August 8, 2025.

Booking 77 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, October is the cheapest month in which you can book a flight from Seattle to Boulder (average of $197). Flying from Seattle to Boulder in March is currently the most expensive (average of $278). 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 August 11, 2025.

Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Seattle to Boulder as you normally would.

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 December 16, 2024.

Travelers seeking maximum savings on their Seattle to Boulder flight should consider departing on Tuesday 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 August 11, 2025.

The most flights from SEA to BD9 are scheduled on a Monday (57 on average). You will have fewer flight options on Tuesday, which is when the least amount of flights are scheduled (34 on average).

How much does it cost to fly round-trip from Seattle to Boulder?

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 August 11, 2025.
See what other customers who have flown with Alaska Airlines, Southwest, and Hawaiian Airlines 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
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Overall

8.0

Entertainment

7.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Alaska Airlines
8.0
Very good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Overall

8.0

Entertainment

7.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Southwest
8.0
Very good
4,246 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Overall

8.0

Entertainment

7.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
Hawaiian Airlines
7.8
Good
2,647 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Overall

8.0

Entertainment

7.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
United Airlines
7.4
Good
8,922 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Overall

8.0

Entertainment

7.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.
American Airlines
7.2
Good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Comfort

7.8

Boarding

8.1

Food

7.1

Crew

8.5

Overall

8.0

Entertainment

7.0

Reviews

1 / 20
10.0
Excellent

Jonathan,Jul 2025

SEA - BOS

Fantastic Check-in with easy baggage drop. While it took a while to find out which was the gate, the boarding was a dream, the stewards were simply incredible and the flight fantastic.

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 46 outbound flights to Boulder per day. You should also have plenty of airline options to choose from since 7 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 291 times in the past calendar month.

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

    To fly one-way, consider booking your trip with Southwest, which is currently one of the cheapest options available, starting at $79. Frontier flights start at $80 while deals on Hawaiian Airlines start at $81 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: ANA (81%), SWISS (77%), United Airlines( 77%).

  • What are the cheapest flights from Seattle to Boulder?

    Looking for the cheapest flight from Seattle to Boulder? While on average our users pay $634, our data indicates the cheapest price to be $80. The most popular route (Seattle/Tacoma Intl - Denver Intl), is priced around $97.

  • 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, October is the cheapest month in which you can book a flight from Seattle to Boulder (average of $197). Flying from Seattle to Boulder in March is currently the most expensive (average of $278). 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

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Alternative routes for Seattle to Boulder

See prices for flight routes from nearby airports that may be better suited for you.
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Top 7 airlines flying from Seattle to Boulder

Discover the top 7 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 August 11, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$62Average$157FlexibilityNo cancel feeOn-time62%
Hawaiian AirlinesCheapest$98Average$234FlexibilityNo cancel feeOn-time85%
DeltaCheapest$108Average$279FlexibilityNo cancel feeOn-timeN/A
SouthwestCheapest$127Average$301FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$148Average$372FlexibilityNo cancel feeOn-time69%
Alaska AirlinesCheapest$166Average$300FlexibilityNo cancel feeOn-time75%
American AirlinesCheapest$169Average$238FlexibilityNo cancel feeOn-time71%

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