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Cheap flights from Washington, D.C. Dulles Intl Airport to Seattle from £124

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 25/9. Fares are subject to change and may not be available on all flights or dates of travel.
IAD — SEA
14 Sep — 21 Sep1
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 August 2026.

Sat 12/907:00 -
Nonstop5h 37m
Tue 22/915:56 -
Nonstop5h 03m
Deal found 12/8£211
Fri 25/915:36 -
1 stop9h 23m
Mon 28/923:14 -
Nonstop5h 03m
Deal found 11/8£215
Fri 11/917:33 -
Nonstop5h 45m
Sat 12/905:00 -
1 stop9h 52m
Deal found 12/8£218
Wed 2/918:00 -
Nonstop5h 45m
Sat 12/908:10 -
Nonstop5h 06m
Deal found 11/8£222
Wed 16/917:15 -
1 stop8h 30m
Sun 20/923:00 -
1 stop7h 23m
Deal found 11/8£226
Fri 11/917:33 -
Nonstop5h 45m
Sun 20/923:04 -
Nonstop5h 03m
Deal found 11/8£226
Thu 24/907:00 -
Nonstop5h 37m
Thu 1/1021:35 -
Nonstop5h 05m
Deal found 10/8£228
Tue 8/912:57 -
Nonstop5h 46m
Fri 18/923:04 -
Nonstop5h 03m
Deal found 11/8£229
Sat 5/917:47 -
Nonstop5h 47m
Mon 14/921:35 -
Nonstop5h 05m
Deal found 12/8£230
Fri 25/919:47 -
1 stop16h 33m
Mon 28/921:35 -
Nonstop5h 05m
Deal found 12/8£233
Sat 5/914:43 -
1 stop9h 48m
Sat 12/908:10 -
Nonstop5h 06m
Deal found 12/8£237

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 August 2026.

Round-trip from

£211

One-way from

£124

Popular in

June

Cheapest in

January

Average price

£325
Alaska Airlines
  • Alaska Airlines
  • 12/9-19/9
  • Nonstop
  • 10h 40m total
  • Washington, D.C. to Seattle
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United Airlines
  • United Airlines
  • 25/9
  • 1 total stop
  • 9h 23m total
  • Washington, D.C. to Seattle
Search Deals
Highest demand for flights based on searches. 21% potential increase in price (£58 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 August 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 15 August 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 Washington, D.C. Dulles Intl - SEA Seattle/Tacoma Intl

IADSEA

Washington, D.C. Dulles Intl

Mon 21/9

17:57-20:44

Nonstop5h 47m

Seattle/Tacoma Intl

Wed 30/9

21:35-05:40

Nonstop5h 05m

£211

Washington, D.C.Seattle

IAD Washington, D.C. Dulles Intl - SEA Seattle/Tacoma Intl

IADSEA

Washington, D.C. Dulles Intl

Wed 30/9

13:05-15:51

Nonstop5h 46m

Seattle/Tacoma Intl

Mon 5/10

23:13-11:55

1 stop9h 42m

£252

Washington, D.C.Seattle

IAD Washington, D.C. Dulles Intl - SEA Seattle/Tacoma Intl

IADSEA

Washington, D.C. Dulles Intl

Sat 5/9

19:35-09:20

1 stop16h 45m

Seattle/Tacoma Intl

Mon 14/9

15:56-23:59

Nonstop5h 03m

£265

Washington, D.C.Seattle

IAD Washington, D.C. Dulles Intl - SEA Seattle/Tacoma Intl

IADSEA

Washington, D.C. Dulles Intl

Sun 13/9

17:33-20:18

Nonstop5h 45m

Seattle/Tacoma Intl

Sat 19/9

08:10-16:16

Nonstop5h 06m

£279
Fastest return journey

Washington, D.C.Seattle

IAD Washington, D.C. Dulles Intl - SEA Seattle/Tacoma Intl

IADSEA

Washington, D.C. Dulles Intl

Tue 15/9

09:03-11:39

Nonstop5h 36m

Seattle/Tacoma Intl

Thu 24/9

21:35-05:40

Nonstop5h 05m

£279

Washington, D.C.Seattle

IAD Washington, D.C. Dulles Intl - SEA Seattle/Tacoma Intl

IADSEA

Washington, D.C. Dulles Intl

Fri 25/9

17:45-20:37

Nonstop5h 52m

Seattle/Tacoma Intl

Sun 4/10

23:14-07:17

Nonstop5h 03m

£279

Washington, D.C.Seattle

IAD Washington, D.C. Dulles Intl - SEA Seattle/Tacoma Intl

IADSEA

Washington, D.C. Dulles Intl

Sat 5/12

17:38-20:26

Nonstop5h 48m

Seattle/Tacoma Intl

Sat 12/12

08:25-16:26

Nonstop5h 01m

£279

Washington, D.C.Seattle

IAD Washington, D.C. Dulles Intl - SEA Seattle/Tacoma Intl

IADSEA

Washington, D.C. Dulles Intl

Thu 5/11

18:46-09:28

1 stop17h 42m

Seattle/Tacoma Intl

Mon 9/11

21:49-05:44

Nonstop4h 55m

£286

Washington, D.C.Seattle

IAD Washington, D.C. Dulles Intl - SEA Seattle/Tacoma Intl

IADSEA

Washington, D.C. Dulles Intl

Sun 27/9

19:47-09:20

1 stop16h 33m

Seattle/Tacoma Intl

Sun 4/10

20:07-17:50

1 stop18h 43m

£294

Washington, D.C.Seattle

IAD Washington, D.C. Dulles Intl - SEA Seattle/Tacoma Intl

IADSEA

Washington, D.C. Dulles Intl

Thu 17/9

19:47-09:20

1 stop16h 33m

Seattle/Tacoma Intl

Sun 20/9

21:35-05:40

Nonstop5h 05m

£297

Flights are sorted by cheapest return flights first.

Deals found on 14/8

Showing 1-10 of 23 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 20 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 £171). Flying from Washington, D.C. Dulles Intl Airport to Seattle in June is currently the most expensive (average of £397). 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 August 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?

Airfare is below average for this route at the moment.

Washington, D.C. Dulles Intl Airport to Seattle flights typically cost between £262 and £427 in September.
The cheapest return price found within the last 5 days was £211 on Alaska Airlines (12 Sept–19 Sept).

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 14 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 5h 46m. Your travel time can differ by up to 10h 59m. 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 (96%), Japan Airlines (90%) and Alaska Airlines (88%).

  • 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 £171). Flying from Washington, D.C. Dulles Intl Airport to Seattle in June is currently the most expensive (average of £397). 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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Federal Way
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Why should you use Cheapflights to find cheap flight tickets from Dulles Intl to Seattle?

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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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