For a smooth check-in at IAD, locate your airline’s counter by walking around the first row if not visible initially.

Most accurate provider | CheapOair 3 stars  | 
|---|---|
Most trusted provider | CheapOair 3 stars  | 
Round-trip from | $237 (Delta)  | 
One-way from | $139 (United Airlines)  | 
Popular in | December | 
Cheapest in | February | 
Average price | $387 | 
Good round-trip deal | $361 or less | 
Good one-way deal | $216 or less | 
Fly from
Fly to
Route
Depart
Return
Price
Washington, D.C.Seattle
IAD - SEA
IADSEA
Washington, D.C. Dulles Intl
Thu 11/27
7:15 am-10:19 am
Nonstop6h 04m
Seattle/Tacoma Intl
Thu 12/4
3:30 pm-11:27 pm
Nonstop4h 57m
Washington, D.C.Seattle
IAD - SEA
IADSEA
Washington, D.C. Dulles Intl
Thu 12/4
6:30 pm-9:30 pm
Nonstop6h 00m
Seattle/Tacoma Intl
Sun 12/7
10:11 pm-6:06 am
Nonstop4h 55m
Washington, D.C.Seattle
IAD - SEA
IADSEA
Washington, D.C. Dulles Intl
Fri 12/5
5:55 pm-8:54 pm
Nonstop5h 59m
Seattle/Tacoma Intl
Sun 12/7
8:10 am-4:18 pm
Nonstop5h 08m
Washington, D.C.Seattle
IAD - SEA
IADSEA
Washington, D.C. Dulles Intl
Mon 12/8
7:15 am-10:12 am
Nonstop5h 57m
Seattle/Tacoma Intl
Sun 12/14
3:30 pm-11:27 pm
Nonstop4h 57m
Washington, D.C.Seattle
IAD - SEA
IADSEA
Washington, D.C. Dulles Intl
Thu 12/4
7:15 am-10:12 am
Nonstop5h 57m
Seattle/Tacoma Intl
Mon 12/8
3:30 pm-11:27 pm
Nonstop4h 57m
Washington, D.C.Seattle
IAD - SEA
IADSEA
Washington, D.C. Dulles Intl
Wed 1/14
7:30 am-10:29 am
Nonstop5h 59m
Seattle/Tacoma Intl
Sun 1/18
3:20 pm-11:10 pm
Nonstop4h 50m
Washington, D.C.Seattle
IAD - SEA
IADSEA
Washington, D.C. Dulles Intl
Fri 12/5
5:55 pm-8:54 pm
Nonstop5h 59m
Seattle/Tacoma Intl
Tue 12/9
7:34 pm-7:30 am
1 stop8h 56m
Washington, D.C.Seattle
IAD - SEA
IADSEA
Washington, D.C. Dulles Intl
Sat 12/6
5:55 pm-8:54 pm
Nonstop5h 59m
Seattle/Tacoma Intl
Wed 12/10
7:34 pm-6:55 am
1 stop8h 21m
Washington, D.C.Seattle
IAD - SEA
IADSEA
Washington, D.C. Dulles Intl
Wed 1/28
7:30 am-10:29 am
Nonstop5h 59m
Seattle/Tacoma Intl
Mon 2/2
3:20 pm-11:10 pm
Nonstop4h 50m
Washington, D.C.Seattle
IAD - SEA
IADSEA
Washington, D.C. Dulles Intl
Fri 12/12
6:30 pm-9:30 pm
Nonstop6h 00m
Seattle/Tacoma Intl
Mon 12/15
10:11 pm-6:06 am
Nonstop4h 55m
| Provider | Price Accuracy | Trust Score* | 
|---|---|---|
| Price Accuracy2 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*1 star | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*2 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy- | Trust Score*1 star | |
| Price Accuracy3 stars | Trust Score*3 stars | 
The price you pay for your flight from Washington, D.C. Dulles Intl Airport to Seattle may vary depending on when you book. For the best chance of a lower fare, look to book 36 days in advance of your trip. Fares are likely to increase a fortnight or so before your departure date.
Currently, April is the cheapest month in which you can book a flight from Washington, D.C. Dulles Intl Airport to Seattle (average of $158). Flying from Washington, D.C. Dulles Intl Airport to Seattle in March is currently the most expensive (average of $243). 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.
One of the essential ways to save on airfare from Washington, D.C. Dulles Intl Airport to Seattle is to remain as flexible as possible. Flights that are in the morning tend to be the most expensive. A flight in the evening could potentially save you up to 18% on airfare.
Travelers seeking maximum savings on their Washington, D.C. Dulles Intl Airport to Seattle flight should consider departing on Tuesday evenings when fares are most often at their lowest. Monday evenings flights should be avoided if possible as fares are typically the most expensive at this time.
Las Vegas (LAS) – chosen by Cheapflights users on 67% of 1-stop itineraries from Washington, D.C. Dulles Intl Airport to Seattle on Cheapflights.
Flights via Denver (DEN) have the shortest average one-way travel time for 1-stop routes: 9h 44m.
Flights via Denver (DEN) have the shortest average one-way travel time for 1-stop routes: 9h 44m.
Flights via Denver (DEN) offer the fastest connection on this route, with an average layover time of 2h 04m.
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Anonymous,Aug 2025
MFR - SEA
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Anonymous,Aug 2025
MFR - SEA
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Anonymous,Aug 2025
MFR - SEA
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Anonymous,Aug 2025
MFR - SEA
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Anonymous,Aug 2025
MFR - SEA
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Anonymous,Aug 2025
MFR - SEA
| Airline | Cheapest | Average | Flexibility | On-time | 
|---|---|---|---|---|
| Cheapest$111 | Average$260 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$149 | Average$393 | FlexibilityNo cancel fee | On-time85% | |
| Cheapest$186 | Average$379 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$275 | Average$436 | FlexibilityNo cancel fee | On-time75% | |
| Cheapest$277 | Average$458 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$321 | Average$527 | FlexibilityNo cancel fee | On-time71% |