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Cheap flights from Washington, D.C. Dulles Intl Airport to Seattle from £128

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
27 Jul — 3 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 27 June 2026.

Tue 14/707:00
IAD
-
SEA
Nonstop5h 45m
Delta
Tue 21/716:05
SEA
-
IAD
Nonstop5h 03m
Delta
Deal found 22/6£247
Sat 15/806:03
IAD
-
SEA
Nonstop5h 45m
Alaska Airlines
Mon 24/819:50
SEA
-
IAD
1 stop19h 24m
Alaska Airlines
Deal found 26/6£249
Sun 9/817:55
IAD
-
SEA
Nonstop5h 51m
United Airlines
Wed 12/818:15
SEA
-
IAD
1 stop8h 10m
United Airlines
Deal found 23/6£250
Wed 12/815:40
IAD
-
SEA
1 stop10h 03m
United Airlines
Wed 19/823:04
SEA
-
IAD
Nonstop5h 03m
United Airlines
Deal found 23/6£251
Mon 14/917:15
IAD
-
SEA
1 stop8h 30m
United Airlines
Sat 19/923:00
SEA
-
IAD
1 stop7h 28m
United Airlines
Deal found 25/6£251
Fri 25/907:00
IAD
-
SEA
Nonstop5h 37m
Alaska Airlines
Mon 5/1015:53
SEA
-
IAD
Nonstop5h 06m
Alaska Airlines
Deal found 27/6£252
Wed 26/807:00
IAD
-
SEA
Nonstop5h 37m
Alaska Airlines
Sat 29/821:35
SEA
-
IAD
Nonstop5h 05m
Alaska Airlines
Deal found 23/6£253
Fri 11/907:00
IAD
-
SEA
Nonstop5h 37m
Alaska Airlines
Wed 30/915:56
SEA
-
IAD
Nonstop5h 03m
Alaska Airlines
Deal found 22/6£254
Sat 15/818:00
IAD
-
SEA
Nonstop5h 45m
United Airlines
Sat 29/823:04
SEA
-
IAD
Nonstop5h 03m
United Airlines
Deal found 23/6£254
Thu 10/907:00
IAD
-
SEA
Nonstop5h 37m
Alaska Airlines
Mon 14/921:35
SEA
-
IAD
Nonstop5h 05m
Alaska Airlines
Deal found 23/6£256
Mon 7/906:30
IAD
-
SEA
1 stop8h 14m
United Airlines
Thu 10/907:00
SEA
-
IAD
1 stop7h 37m
United Airlines
Deal found 24/6£257

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 27 June 2026.

Round-trip from

£247

One-way from

£128

Popular in

June

Cheapest in

January

Average price

£408
Delta
  • Delta
  • 14/7-21/7
  • Nonstop
  • 10h 48m 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 (£56 potential increase over avg. return price).
Search Deals
Cheapest flight prices on average. 3% potential price decrease (£9 potential savings vs. average return price).
Search Deals
Average for round-trip flights in June 2026
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 27 June 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 24/8

07:00-09:37

Nonstop5h 37m

Seattle/Tacoma Intl

Tue 1/9

21:35-05:40

Nonstop5h 05m

£254
Fastest return journey

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Thu 10/9

09:03-11:39

Nonstop5h 36m

Seattle/Tacoma Intl

Mon 14/9

21:35-05:40

Nonstop5h 05m

£256

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Sun 16/8

06:15-11:32

1 stop8h 17m

Seattle/Tacoma Intl

Mon 24/8

23:00-09:28

1 stop7h 28m

£258

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Sat 29/8

07:10-09:55

Nonstop5h 45m

Seattle/Tacoma Intl

Fri 4/9

15:58-23:59

Nonstop5h 01m

£270

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Tue 14/7

07:00-09:45

Nonstop5h 45m

Seattle/Tacoma Intl

Wed 22/7

16:05-00:08

Nonstop5h 03m

£270

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Thu 20/8

07:00-09:37

Nonstop5h 37m

Seattle/Tacoma Intl

Wed 2/9

20:49-18:14

1 stop18h 25m

£270

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Tue 25/8

09:03-11:39

Nonstop5h 36m

Seattle/Tacoma Intl

Mon 31/8

19:50-18:14

1 stop19h 24m

£272

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Wed 26/8

07:00-09:37

Nonstop5h 37m

Seattle/Tacoma Intl

Mon 31/8

19:50-18:14

1 stop19h 24m

£272

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Sat 29/8

18:00-20:45

Nonstop5h 45m

Seattle/Tacoma Intl

Wed 2/9

13:57-00:44

1 stop7h 47m

£284

Washington, D.C.Seattle

IAD - SEA

IADSEA

Washington, D.C. Dulles Intl

Mon 24/8

18:00-20:45

Nonstop5h 45m

Seattle/Tacoma Intl

Sat 29/8

07:00-18:59

1 stop8h 59m

£284

Flights are sorted by cheapest return flights first.

Deals found on 23/6

Showing 1-10 of 24 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 52 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 £175). Flying from Washington, D.C. Dulles Intl Airport to Seattle in June is currently the most expensive (average of £406). 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 27 June 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 21 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?

    Alaska Airlines, United Airlines, and Delta can get you from Washington, D.C. Dulles Intl Airport to Seattle in just under 5h 37m. Your travel time can differ by up to 2h 40m. 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 (95%) and China Eastern (89%).

  • 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 £175). Flying from Washington, D.C. Dulles Intl Airport to Seattle in June is currently the most expensive (average of £406). 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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