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Cheap flights from Washington, D.C. Dulles Intl Airport to Seattle from £129

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 10/8. Fares are subject to change and may not be available on all flights or dates of travel.
IAD — SEA
14 Aug — 21 Aug1
1 adult
1 adult, Economy, 0 bags

Cheap flight deals from Dulles Intl to Seattle

Enter your travel dates to find the best prices.

Cheapest flights from Dulles Intl to Seattle
Explore the most affordable flight options available from Dulles Intl to Seattle. Find the lowest fares from popular airlines and budget airlines, with prices last updated on 15 July 2026.

Fri 28/807:00
IAD
-
SEA
Nonstop5h 37m
Alaska Airlines
Fri 4/921:35
SEA
-
IAD
Nonstop5h 05m
Alaska Airlines
Deal found 14/7£231
Mon 21/907:00
IAD
-
SEA
Nonstop5h 37m
Alaska Airlines
Thu 24/921:35
SEA
-
IAD
Nonstop5h 05m
Alaska Airlines
Deal found 14/7£232
Thu 27/808:59
IAD
-
SEA
1 stop10h 29m
Multiple Airlines
Thu 3/915:56
SEA
-
IAD
Nonstop5h 03m
Multiple Airlines
Deal found 13/7£232
Thu 27/817:47
IAD
-
SEA
Nonstop5h 47m
Alaska Airlines
Thu 3/915:56
SEA
-
IAD
Nonstop5h 03m
Alaska Airlines
Deal found 13/7£234
Thu 27/817:15
IAD
-
SEA
1 stop8h 28m
United Airlines
Mon 31/823:00
SEA
-
IAD
1 stop7h 28m
United Airlines
Deal found 14/7£235
Fri 25/907:00
IAD
-
SEA
Nonstop5h 37m
Alaska Airlines
Mon 5/1021:05
SEA
-
IAD
1 stop17h 48m
Alaska Airlines
Deal found 13/7£236
Sat 22/818:00
IAD
-
SEA
Nonstop5h 45m
United Airlines
Tue 25/808:10
SEA
-
IAD
Nonstop5h 06m
United Airlines
Deal found 14/7£238
Wed 2/909:03
IAD
-
SEA
Nonstop5h 36m
Alaska Airlines
Mon 14/921:35
SEA
-
IAD
Nonstop5h 05m
Alaska Airlines
Deal found 11/7£238
Mon 24/813:20
IAD
-
SEA
Nonstop5h 46m
United Airlines
Mon 31/823:04
SEA
-
IAD
Nonstop5h 03m
United Airlines
Deal found 14/7£240
Sat 22/807:00
IAD
-
SEA
Nonstop5h 37m
Alaska Airlines
Mon 24/820:49
SEA
-
IAD
1 stop18h 25m
Alaska Airlines
Deal found 11/7£241
Sat 15/818:14
IAD
-
SEA
Nonstop5h 55m
Alaska Airlines
Mon 24/820:49
SEA
-
IAD
1 stop18h 25m
Alaska Airlines
Deal found 14/7£241
Tue 25/813:20
IAD
-
SEA
Nonstop5h 46m
United Airlines
Sun 30/823:00
SEA
-
IAD
1 stop7h 23m
United Airlines
Deal found 14/7£242

Find flight deals from Dulles Intl to Seattle

Discover tips and strategies to find the most affordable flight options for your journey from Dulles Intl (IAD) to Seattle (SEA). Learn about various techniques such as flexible date searches, comparing prices across and setting up price alerts. Use these methods to find the cheapest flights available for your travel needs. Data last updated 15 July 2026.

Round-trip from

£231

One-way from

£129

Popular in

June

Cheapest in

January

Average price

£370

Good one-way deal

£141 or less
Alaska Airlines
  • Alaska Airlines
  • 28/8-4/9
  • Nonstop
  • 10h 42m total
  • Washington, D.C. to Seattle
Search Deals
United Airlines
  • United Airlines
  • 10/8
  • Nonstop
  • 5h 51m total
  • Washington, D.C. to Seattle
Search Deals
Highest demand for flights based on searches. 20% potential increase in price (£57 potential increase over avg. return price).
Search Deals
Cheapest flight prices on average. 3% potential price decrease (£8 potential savings vs. average return price).
Search Deals
Average for round-trip flights in July 2026
Search Deals
Price to beat on a one-way flight from Washington, D.C. Dulles Intl to Seattle/Tacoma Intl.
Search Deals

Cheapflights Fare Finder

 
Customise your flight search to find flights from Dulles Intl to Seattle 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 858,174 searches. Data last updated 15 July 2026.
Use the filters below to find and compare flights from Washington, D.C. Dulles Intl Airport to Seattle that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest return flight

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Mon 21/9

17:15-22:45

1 stop8h 30m

Seattle/Tacoma Intl

Thu 1/10

07:00-17:44

1 stop7h 44m

£259

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Sun 16/8

19:53-09:19

1 stop16h 26m

Seattle/Tacoma Intl

Mon 24/8

20:49-18:14

1 stop18h 25m

£265
Fastest return journey

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Tue 13/10

13:05-15:51

Nonstop5h 46m

Seattle/Tacoma Intl

Sun 18/10

23:14-07:17

Nonstop5h 03m

£267

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Sun 8/11

07:46-10:38

Nonstop5h 52m

Seattle/Tacoma Intl

Sat 14/11

21:53-05:51

Nonstop4h 58m

£267

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Tue 13/10

17:45-20:37

Nonstop5h 52m

Seattle/Tacoma Intl

Mon 19/10

08:10-16:16

Nonstop5h 06m

£267

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Fri 4/9

19:35-09:20

1 stop16h 45m

Seattle/Tacoma Intl

Wed 9/9

20:40-18:14

1 stop18h 34m

£280

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Wed 5/8

19:53-09:19

1 stop16h 26m

Seattle/Tacoma Intl

Thu 13/8

06:21-18:45

1 stop9h 24m

£280

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Mon 21/9

15:40-22:45

1 stop10h 05m

Seattle/Tacoma Intl

Mon 28/9

23:14-07:17

Nonstop5h 03m

£280

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Wed 26/8

15:40-22:43

1 stop10h 03m

Seattle/Tacoma Intl

Mon 31/8

15:30-05:55

1 stop11h 25m

£288

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Mon 21/9

17:15-22:45

1 stop8h 30m

Seattle/Tacoma Intl

Tue 29/9

10:55-22:09

1 stop8h 14m

£288

Flights are sorted by cheapest return flights first.

Deals found on 12/7

Showing 1-10 of 22 resultsSorted by cheapest first
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Best time to book a flight from Dulles Intl to Seattle

Have a flexible travel schedule? Discover the best time to fly to Seattle from Dulles Intl with our price prediction graph.
Estimated return 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 Washington, D.C. Dulles Intl Airport to Seattle

How far ahead should I book a flight from Washington, D.C. Dulles Intl Airport to Seattle?

The best time to book flights from Washington, D.C. Dulles Intl Airport to Seattle is 34 days before your desired departure date. The cost of your flight will likely increase significantly if you book two weeks in advance of your flight.

What is the cheapest month to book a flight from Washington, D.C. Dulles Intl Airport to Seattle?

Currently, January is the cheapest month in which you can book a flight from Washington, D.C. Dulles Intl Airport to Seattle (average of £173). Flying from Washington, D.C. Dulles Intl Airport to Seattle in June is currently the most expensive (average of £401). 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 IAD to SEA?

Find hourly flight availability from Dulles Intl to Seattle. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated 15 July 2026.

When flying from Washington, D.C. Dulles Intl Airport to Seattle, the time of day you decide to fly out makes little to no difference towards the overall price you’ll pay on tickets.

How much does it cost for a return flight from Washington, D.C. Dulles Intl Airport to Seattle?

Related info for your journey

Find useful and relevant information for your journey from Dulles Intl to Seattle. 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 into for flights to Seattle from Washington, D.C. Dulles Intl?

    Located just 11.4 mi from the city center, Seattle/Tacoma Intl is the airport most travelers will use when flying to Seattle from Washington, D.C. Dulles Intl. Booking flights from Washington, D.C. Dulles Intl to Seattle/Tacoma Intl (SEA) should be relatively easy as there are 22 daily inbound flights from Washington, D.C. Dulles Intl from 0 different airlines.

  • How long is the flight from Washington, D.C. Dulles Intl Airport to Seattle?

    United Airlines and Alaska Airlines can get you from Washington, D.C. Dulles Intl Airport to Seattle in just under 8h 30m. Your travel time can differ by up to 7h 56m. The distance from Washington, D.C. Dulles Intl Airport to Seattle is about 2299 mi. When browsing for deals, the options you’ll see will be for both direct flights and flights with stops.

  • What are the most reliable airlines from Washington, D.C. Dulles Intl Airport to Seattle?

    The top 3 most reliable airlines when flying from Washington, D.C. Dulles Intl Airport to Seattle are Finnair (100%), Japan Airlines (90%) and Ethiopian Air (85%).

  • What are the cheapest flights from Washington, D.C. Dulles Intl Airport to Seattle?

    Looking for the cheapest flight from Washington, D.C. Dulles Intl Airport to Seattle? While on average our users pay £181, our data indicates the cheapest price to be £141. The most popular route (Washington, D.C. Dulles Intl - Seattle/Tacoma Intl), is priced around £274.

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

    Yes. In addition to deals on Dulles Intl to Seattle flights, Cheapflights offers holiday packages that include both flights and hotel.

  • How can I find direct flights from Dulles Intl to Seattle?

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

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

    Yes. Cheapflights offers flight deals from Dulles Intl to Seattle 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 Washington, D.C. Dulles Intl Airport to Seattle?

    Currently, January is the cheapest month in which you can book a flight from Washington, D.C. Dulles Intl Airport to Seattle (average of £173). Flying from Washington, D.C. Dulles Intl Airport to Seattle in June is currently the most expensive (average of £401). 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

Travelling to a place near Seattle?

Book flights to Seattle if you plan to visit one of these locations
Tacoma
Federal Way
SeaTac

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Why should you use Cheapflights to find cheap flight tickets from Dulles Intl to Seattle?

Cheapflights simply makes it quick and affordable to book flights from Dulles Intl to Seattle by bringing together all flight options from hundreds of airlines and agencies online — and put it in one place for you to choose from. Plus, Cheapflights is 100% free to use for all.

Can Cheapflights find flights from Dulles Intl to Seattle with no change fees?

Need flexible booking options for your flight to Seattle from Dulles Intl? Don’t worry, Cheapflights have you covered. Use our search filter to only show flights with no change fees.

Can Cheapflights notify me if prices for flights from Dulles Intl to Seattle become cheaper?

Yes, Cheapflights offers price alerts on Dulles Intl to Seattle flights so you can book your travel at the perfect time. Price Alerts can be enabled by clicking the bell icon next to the flight deals above and providing your email address where you want to receive the alerts.

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