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$63+ 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 5/1. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — DEN
May 2 — May 91
Sat 5/2
Sat 5/9
1 adult, Economy
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Cheapflights Tip: The best prices from Seattle/Tacoma Intl to Boulder are usually found in January or October, booked 66 days in advance, depart on a Friday or Saturday and return on a Friday

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 April 2, 2026.

This Kiwi.com deal was found by Cheapflights users on 3/31. 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.
Tue 4/147:12 pm
SEA
-
DEN
Nonstop2h 47m
Frontier
Tue 4/217:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 3/31$92
This Cheapflightsfares deal was found by Cheapflights users on 3/31. 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 4/158:07 pm
SEA
-
DEN
Nonstop2h 52m
Frontier
Tue 4/217:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 3/31$93
This Super.com deal was found by Cheapflights users on 3/31. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 4/217:12 pm
SEA
-
DEN
Nonstop2h 47m
Frontier
Tue 4/287:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 3/31$97
This Frontier deal was found by Cheapflights users on 3/30. 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.
Tue 4/217:12 pm
SEA
-
DEN
Nonstop2h 47m
Frontier
Wed 4/227:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 3/30$98
This Cheapflightsfares deal was found by Cheapflights users on 3/31. 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 4/158:07 pm
SEA
-
DEN
Nonstop2h 52m
Frontier
Sat 4/257:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 3/31$102
This Frontier deal was found by Cheapflights users on 3/31. 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 4/257:12 pm
SEA
-
DEN
Nonstop2h 47m
Frontier
Wed 4/297:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 3/31$103
This Kiwi.com deal was found by Cheapflights users on 4/2. 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 4/158:07 pm
SEA
-
DEN
Nonstop2h 52m
Frontier
Wed 4/297:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 4/2$106
This Super.com deal was found by Cheapflights users on 3/28. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 4/257:12 pm
SEA
-
DEN
Nonstop2h 47m
Frontier
Sat 5/27:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 3/28$107
This Kiwi.com deal was found by Cheapflights users on 4/2. 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 4/158:07 pm
SEA
-
DEN
Nonstop2h 52m
Frontier
Sat 5/27:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 4/2$111
This Cheapflightsfares deal was found by Cheapflights users on 3/31. 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 5/14:20 pm
SEA
-
DEN
Nonstop2h 51m
Frontier
Tue 5/57:50 am
DEN
-
SEA
Nonstop2h 59m
Frontier
Deal found 3/31$112
This Frontier deal was found by Cheapflights users on 3/31. 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.
Tue 4/217:12 pm
SEA
-
DEN
Nonstop2h 47m
Frontier
Mon 4/277:15 am
DEN
-
SEA
Nonstop3h 12m
Frontier
Deal found 3/31$113

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 April 2, 2026.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$92
(Kiwi.com)

One-way from

$63
(Super.com)

Popular in

June

Cheapest in

January

Average price

$217
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 ($21 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 1% potential price decrease ($4 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in April 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 April 2, 2026.
Use the filters below to find and compare flights from Seattle to Boulder that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest round-trip
Quickest round-trip

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sat 5/9

7:50 am-11:49 am

Nonstop2h 59m

Denver Intl

Mon 5/11

6:05 am-8:09 am

Nonstop3h 04m

$227

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sat 5/9

6:00 pm-9:49 pm

Nonstop2h 49m

Denver Intl

Tue 5/12

1:02 pm-9:45 pm

1 stop9h 43m

$227

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Wed 4/22

9:20 am-1:00 pm

Nonstop2h 40m

Denver Intl

Wed 4/29

1:45 pm-10:55 pm

2 stops10h 10m

$232

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Thu 4/23

11:05 am-7:00 pm

1 stop6h 55m

Denver Intl

Sat 4/25

2:55 pm-10:30 pm

2 stops8h 35m

$252

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sat 4/25

12:01 pm-4:02 pm

Nonstop3h 01m

Denver Intl

Tue 4/28

1:02 pm-7:57 pm

1 stop7h 55m

$266

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Sat 5/16

6:25 am-2:40 pm

2 stops7h 15m

Denver Intl

Tue 5/19

10:40 am-6:00 pm

1 stop8h 20m

$272

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Mon 5/4

1:17 pm-5:11 pm

Nonstop2h 54m

Denver Intl

Wed 5/6

11:46 am-6:36 pm

1 stop7h 50m

$292

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Thu 5/28

9:40 am-6:05 pm

2 stops7h 25m

Denver Intl

Mon 6/1

4:25 pm-11:05 pm

2 stops7h 40m

$302

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Tue 9/22

5:24 am-10:39 am

1 stop4h 15m

Denver Intl

Sat 9/26

8:20 am-2:54 pm

1 stop7h 34m

$315

SeattleDenver

SEA - DEN

SEADEN

Seattle/Tacoma Intl

Mon 4/27

7:05 am-10:54 am

Nonstop2h 49m

Denver Intl

Wed 4/29

6:45 am-2:14 pm

2 stops8h 29m

$320

Flights are sorted by cheapest round-trip flights first.

Deals found on 4/1

Showing 1-10 of 23 resultsSorted by cheapest first
1
2
3

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 April 2, 2026.

Booking 66 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 $37). Flying from Seattle to Boulder in July is currently the most expensive (average of $100). 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 April 2, 2026.

Unlike in the morning, when flights are generally more expensive, you can save up to 22% 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 March 28, 2026.

Travelers seeking maximum savings on their Seattle to Boulder flight should consider departing on Friday evenings when fares are most often at their lowest. Sunday 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 April 2, 2026.

The most flights from SEA to BD9 are scheduled on a Thursday (35 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (9 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 April 2, 2026.
See what other customers who have flown with Southwest,Alaska Airlines, andDelta 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.
Southwest
8.0
Very good
4,337 reviews

Boarding

8.1

Crew

8.6

Comfort

8.0

Entertainment

7.5

Food

7.0

Overall

8.0

Reviews

1 / 20
2.0
Mediocre

Dominic,Mar 2026

MCO - SMF

I had to try and sleep on the floor of the Austin airport. I spent 12 hours there. The airline policies were so poor, that a near violent argument broke out between the people in front of me and the flight attendants - making for a super stressful situation at 30,000 feet. Garbage airline choice by Kayak Garbage idea to book a flight with a layover. Next time I will pay for a quality booking myself, and somehow force the company to reimburse it.
Southwest
8.0
Very good
4,337 reviews
Southwest
8.0
Very good
4,337 reviews

Boarding

8.1

Crew

8.6

Comfort

8.0

Entertainment

7.5

Food

7.0

Overall

8.0

Reviews

1 / 20
2.0
Mediocre

Dominic,Mar 2026

MCO - SMF

I had to try and sleep on the floor of the Austin airport. I spent 12 hours there. The airline policies were so poor, that a near violent argument broke out between the people in front of me and the flight attendants - making for a super stressful situation at 30,000 feet. Garbage airline choice by Kayak Garbage idea to book a flight with a layover. Next time I will pay for a quality booking myself, and somehow force the company to reimburse it.
Alaska Airlines
7.9
Good
12,152 reviews
Southwest
8.0
Very good
4,337 reviews

Boarding

8.1

Crew

8.6

Comfort

8.0

Entertainment

7.5

Food

7.0

Overall

8.0

Reviews

1 / 20
2.0
Mediocre

Dominic,Mar 2026

MCO - SMF

I had to try and sleep on the floor of the Austin airport. I spent 12 hours there. The airline policies were so poor, that a near violent argument broke out between the people in front of me and the flight attendants - making for a super stressful situation at 30,000 feet. Garbage airline choice by Kayak Garbage idea to book a flight with a layover. Next time I will pay for a quality booking myself, and somehow force the company to reimburse it.
Delta
7.9
Good
8,370 reviews
Southwest
8.0
Very good
4,337 reviews

Boarding

8.1

Crew

8.6

Comfort

8.0

Entertainment

7.5

Food

7.0

Overall

8.0

Reviews

1 / 20
2.0
Mediocre

Dominic,Mar 2026

MCO - SMF

I had to try and sleep on the floor of the Austin airport. I spent 12 hours there. The airline policies were so poor, that a near violent argument broke out between the people in front of me and the flight attendants - making for a super stressful situation at 30,000 feet. Garbage airline choice by Kayak Garbage idea to book a flight with a layover. Next time I will pay for a quality booking myself, and somehow force the company to reimburse it.
United Airlines
7.4
Good
9,533 reviews
Southwest
8.0
Very good
4,337 reviews

Boarding

8.1

Crew

8.6

Comfort

8.0

Entertainment

7.5

Food

7.0

Overall

8.0

Reviews

1 / 20
2.0
Mediocre

Dominic,Mar 2026

MCO - SMF

I had to try and sleep on the floor of the Austin airport. I spent 12 hours there. The airline policies were so poor, that a near violent argument broke out between the people in front of me and the flight attendants - making for a super stressful situation at 30,000 feet. Garbage airline choice by Kayak Garbage idea to book a flight with a layover. Next time I will pay for a quality booking myself, and somehow force the company to reimburse it.
Frontier
5.7
Fair
3,004 reviews
Southwest
8.0
Very good
4,337 reviews

Boarding

8.1

Crew

8.6

Comfort

8.0

Entertainment

7.5

Food

7.0

Overall

8.0

Reviews

1 / 20
2.0
Mediocre

Dominic,Mar 2026

MCO - SMF

I had to try and sleep on the floor of the Austin airport. I spent 12 hours there. The airline policies were so poor, that a near violent argument broke out between the people in front of me and the flight attendants - making for a super stressful situation at 30,000 feet. Garbage airline choice by Kayak Garbage idea to book a flight with a layover. Next time I will pay for a quality booking myself, and somehow force the company to reimburse it.

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 21 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 263 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 40m. Fly via Delta, Alaska Airlines, or Southwest 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 $58 while deals on Delta start at $62 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: Condor (92%), United Airlines (90%), STARLUX Airlines( 88%).

  • What are the cheapest flights from Seattle to Boulder?

    Looking for the cheapest flight from Seattle to Boulder? While on average our users pay $715, our data indicates the cheapest price to be $58. The most popular route (Seattle/Tacoma Intl - Denver Intl), is priced around $93.

  • 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 $37). Flying from Seattle to Boulder in July is currently the most expensive (average of $100). 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

Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.

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 April 2, 2026.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$57Average$167FlexibilityNo cancel feeOn-time62%
Hawaiian AirlinesCheapest$78Average$222FlexibilityNo cancel feeOn-time85%
DeltaCheapest$95Average$244FlexibilityNo cancel feeOn-timeN/A
Alaska AirlinesCheapest$117Average$283FlexibilityNo cancel feeOn-time75%
SouthwestCheapest$117Average$309FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$130Average$396FlexibilityNo cancel feeOn-time69%

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