HomeSearch by dateVacation packagesHotelsFlight dealsCar rentalTravel tips & news
Ontario

$153+ Cheap flights from Seattle (SEA) to Ontario

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 9/28. Fares are subject to change and may not be available on all flights or dates of travel.
SEA — YYZ
Aug 27 — Sep 31
Thu 8/27
Thu 9/3
1 adult, Economy
We work with more than 300 partners to bring you better travel deals

Find cheap flights from Seattle to Ontario with Cheapflights

1. Tell us where you want to go

Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”

2. Select your favorite providers

We find the providers serving your travel needs. Choose up to four travel providers to compare side-by-side for flights, hotels, or car rentals.

3. Compare prices and book

Review each provider’s pricing and select the best option for you! Book through your favorite provider’s website for a seamless experience.

Cheap flight deals from Seattle to Ontario

Cheapest flights from Seattle to Ontario
Explore the most affordable flight options available from Seattle to Ontario. Find the lowest fares from popular airlines and budget airlines, with prices last updated on July 28, 2026.

This Trip.com deal was found by Cheapflights users on 7/25. 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 Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 9/247:35 pm
SEA
-
YOW
1 stop7h 00m
WestJet
Mon 9/2812:25 pm
YOW
-
SEA
2 stops9h 20m
WestJet
Deal found 7/25$346
This Kiwi.com deal was found by Cheapflights users on 7/26. 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 9/157:35 pm
SEA
-
YOW
1 stop7h 00m
WestJet
Sat 9/261:20 pm
YOW
-
SEA
1 stop8h 25m
WestJet
Deal found 7/26$369
This FlightHub deal was found by Cheapflights users on 7/27. 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 FlightHub is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/2610:30 am
SEA
-
YYZ
1 stop9h 15m
WestJet
Wed 9/22:50 pm
YYZ
-
SEA
1 stop9h 10m
WestJet
Deal found 7/27$375
This Mytrip deal was found by Cheapflights users on 7/27. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 9/2410:30 am
SEA
-
YYZ
1 stop7h 45m
WestJet
Sun 9/273:30 pm
YYZ
-
SEA
2 stops21h 10m
WestJet
Deal found 7/27$379
This FlightHub deal was found by Cheapflights users on 7/27. 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 FlightHub is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/197:35 pm
SEA
-
YYZ
1 stop7h 10m
WestJet
Sun 10/410:20 pm
YYZ
-
SEA
2 stops14h 20m
WestJet
Deal found 7/27$380
This Mytrip deal was found by Cheapflights users on 7/27. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/227:35 pm
SEA
-
YOW
1 stop7h 00m
WestJet
Sat 10/246:55 am
YOW
-
SEA
2 stops14h 50m
WestJet
Deal found 7/27$382
This Kiwi.com deal was found by Cheapflights users on 7/23. 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.
Fri 8/2810:30 am
SEA
-
YYZ
2 stops10h 29m
WestJet
Sun 9/61:30 pm
YYZ
-
SEA
1 stop8h 15m
WestJet
Deal found 7/23$384
This Kiwi.com deal was found by Cheapflights users on 7/23. 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.
Mon 9/287:35 pm
SEA
-
YYZ
1 stop7h 10m
WestJet
Wed 10/710:20 pm
YYZ
-
SEA
2 stops14h 20m
WestJet
Deal found 7/23$385
This oojo deal was found by Cheapflights users on 7/27. 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 oojo is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/97:35 pm
SEA
-
YOW
1 stop7h 00m
WestJet
Sat 9/191:20 pm
YOW
-
SEA
1 stop8h 25m
WestJet
Deal found 7/27$385
This Kiwi.com deal was found by Cheapflights users on 7/24. 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 8/257:00 am
SEA
-
YYZ
1 stop7h 10m
WestJet
Wed 9/23:50 pm
YYZ
-
SEA
1 stop8h 10m
WestJet
Deal found 7/24$386
This Kiwi.com deal was found by Cheapflights users on 7/25. 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.
Sun 9/137:35 pm
SEA
-
YYZ
1 stop7h 10m
WestJet
Tue 10/1310:20 pm
YYZ
-
SEA
2 stops14h 20m
WestJet
Deal found 7/25$387
This Kiwi.com deal was found by Cheapflights users on 7/24. 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 8/1110:30 am
SEA
-
YYZ
1 stop7h 45m
WestJet
Fri 8/2112:00 pm
YYZ
-
SEA
2 stops12h 00m
WestJet
Deal found 7/24$388

Find flight deals from Seattle to Ontario

Keep the following information in mind while searching for Seattle to Ontario flight deals. Data was last updated July 28, 2026.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$346
(Trip.com)

One-way from

$153
(Kiwi.com)

Popular in

July

Cheapest in

January

Average price

$647

Good round-trip deal

$498 or less

Good one-way deal

$293 or less
Provider with most accurate pricing for Seattle/Tacoma Intl-Toronto (YTO) flight deals.
Search Deals
Provider most trusted by Cheapflights users for Seattle/Tacoma Intl-Toronto (YTO) flights.
Search Deals
From Seattle/Tacoma Intl to Ontario
Search Deals
One-way flight from Seattle/Tacoma Intl to Ontario
Search Deals
Highest demand for flights based on searches. 26% potential increase in price ($150 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 5% potential price decrease ($21 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in July 2026
Search Deals
Price to beat on a round-trip flight from Seattle/Tacoma Intl to Ontario.
Search Deals
Price to beat on a one-way flight from Seattle/Tacoma Intl to Ontario.
Search Deals

Cheapflights Fare Finder

 
Customize your flight search to find flights from Seattle to Ontario 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 July 28, 2026.
Use the filters below to find and compare flights from Seattle to Ontario that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest round-trip

SeattleOttawa

SEA - YOW

SEAYOW

Seattle/Tacoma Intl

Thu 9/24

7:35 pm-5:35 am

1 stop7h 00m

Ottawa

Mon 9/28

8:15 pm-9:40 am

1 stop16h 25m

$370

SeattleHamilton

SEA - YHM

SEAYHM

Seattle/Tacoma Intl

Sun 8/23

7:00 am-5:15 pm

1 stop7h 15m

Hamilton

Tue 8/25

6:10 pm-9:40 am

1 stop18h 30m

$413

SeattleHamilton

SEA - YHM

SEAYHM

Seattle/Tacoma Intl

Sun 8/23

7:00 am-5:15 pm

1 stop7h 15m

Hamilton

Wed 8/26

6:10 pm-9:40 am

1 stop18h 30m

$413

SeattleOttawa

SEA - YOW

SEAYOW

Seattle/Tacoma Intl

Fri 10/16

7:35 pm-5:35 am

1 stop7h 00m

Ottawa

Sun 10/18

6:55 am-6:45 pm

2 stops14h 50m

$421

SeattleToronto

SEA - YKF

SEAYKF

Seattle/Tacoma Intl

Tue 10/13

7:35 pm-7:50 pm

1 stop21h 15m

Toronto Region of Waterloo Intl

Fri 10/16

8:40 pm-6:45 pm

1 stop25h 05m

$422

SeattleToronto

SEA - YKF

SEAYKF

Seattle/Tacoma Intl

Sat 10/10

7:35 pm-7:50 pm

1 stop21h 15m

Toronto Region of Waterloo Intl

Mon 10/12

8:40 pm-6:45 pm

1 stop25h 05m

$422

SeattleToronto

SEA - YKF

SEAYKF

Seattle/Tacoma Intl

Sat 10/3

7:35 pm-7:50 pm

1 stop21h 15m

Toronto Region of Waterloo Intl

Sun 10/11

8:40 pm-9:40 am

1 stop16h 00m

$423

SeattleToronto

SEA - YKF

SEAYKF

Seattle/Tacoma Intl

Wed 8/12

7:00 am-7:50 pm

1 stop9h 50m

Toronto Region of Waterloo Intl

Sat 8/15

8:40 pm-9:40 am

1 stop16h 00m

$430

SeattleMontreal

SEA - YUL

SEAYUL

Seattle/Tacoma Intl

Wed 9/16

11:35 am-11:50 pm

1 stop9h 15m

Montreal Pierre Elliott Trudeau Intl

Tue 9/22

12:48 pm-6:45 pm

1 stop8h 57m

$436

SeattleMontreal

SEA - YUL

SEAYUL

Seattle/Tacoma Intl

Wed 9/9

9:43 am-11:27 pm

1 stop10h 44m

Montreal Pierre Elliott Trudeau Intl

Sat 9/12

7:00 am-4:45 pm

1 stop12h 45m

$436

Flights are sorted by cheapest round-trip flights first.

Deals found on 7/26

Showing 1-10 of 60 resultsSorted by cheapest first
1
2
3
...
6

Best time to book a flight from Seattle to Ontario

Have a flexible travel schedule? Discover the best time to fly to Ontario 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 Ontario

What is the cheapest month to book a flight from Seattle to Region of Ontario?

Currently, January is the cheapest month in which you can book a flight from Seattle to Region of Ontario (average of $274). Flying from Seattle to Region of Ontario in July is currently the most expensive (average of $600). 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 ON?

Find hourly flight availability from Seattle to Ontario. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated July 28, 2026.

Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Seattle to Region of Ontario as you normally would.

Weekly flight availability from Seattle to Region of Ontario

Explore weekly flight availability from Seattle to Ontario. 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 July 28, 2026.

The most flights from SEA to CAON are scheduled on a Sunday (7 on average). You will have fewer flight options on Tuesday, which is when the least amount of flights are scheduled (4 on average).

How much does it cost to fly round-trip from Seattle to Region of Ontario?

Airfare is below average for this route at the moment.
Seattle to Region of Ontario flights typically cost between $389 and $740 in August.
The cheapest round-trip price found within the last 5 days was $375 on WestJet (Aug 26-Sep 2).

How far ahead should I book a flight from Seattle to Region of Ontario?

The price you pay for your flight from Seattle to Region of Ontario may vary depending on when you book. For the best chance of a lower fare, look to book 59 days in advance of your trip. Fares are likely to increase a fortnight or so before your departure date.

Reviews of airlines servicing Ontario

Get insights into the airlines that provide service to Ontario. 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 Ontario. Reviews last updated July 28, 2026.
Read through reviews of airlines operating flights from Seattle to Ontario, such as Alaska Airlines,Delta, andUnited Airlines. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
7.9
Good
12,721 reviews

Overall

7.9

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.0

Reviews

1 / 20
6.0
Good

Anonymous,Jul 2026

SEA - LHR

Alaska has a brilliant crew. And the seats are good. As much as i loved my trip from Heathrow to Seattle, i definitely did not feel the same on the return flight. A lot was due to feeling very cramped and unfortunately for me, i had a kicker behind me and a passenger who did not stop moving (but constantly) next to me. The good was not good and i noticed that most people around me left most of their meal. The ice cream was very nice. I did not have breakfast. However the food was very nice on the way to Seattle
Alaska Airlines
7.9
Good
12,721 reviews
Alaska Airlines
7.9
Good
12,721 reviews

Overall

7.9

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.0

Reviews

1 / 20
6.0
Good

Anonymous,Jul 2026

SEA - LHR

Alaska has a brilliant crew. And the seats are good. As much as i loved my trip from Heathrow to Seattle, i definitely did not feel the same on the return flight. A lot was due to feeling very cramped and unfortunately for me, i had a kicker behind me and a passenger who did not stop moving (but constantly) next to me. The good was not good and i noticed that most people around me left most of their meal. The ice cream was very nice. I did not have breakfast. However the food was very nice on the way to Seattle
Delta
7.8
Good
8,480 reviews
Alaska Airlines
7.9
Good
12,721 reviews

Overall

7.9

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.0

Reviews

1 / 20
6.0
Good

Anonymous,Jul 2026

SEA - LHR

Alaska has a brilliant crew. And the seats are good. As much as i loved my trip from Heathrow to Seattle, i definitely did not feel the same on the return flight. A lot was due to feeling very cramped and unfortunately for me, i had a kicker behind me and a passenger who did not stop moving (but constantly) next to me. The good was not good and i noticed that most people around me left most of their meal. The ice cream was very nice. I did not have breakfast. However the food was very nice on the way to Seattle
United Airlines
7.4
Good
10,046 reviews
Alaska Airlines
7.9
Good
12,721 reviews

Overall

7.9

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.0

Reviews

1 / 20
6.0
Good

Anonymous,Jul 2026

SEA - LHR

Alaska has a brilliant crew. And the seats are good. As much as i loved my trip from Heathrow to Seattle, i definitely did not feel the same on the return flight. A lot was due to feeling very cramped and unfortunately for me, i had a kicker behind me and a passenger who did not stop moving (but constantly) next to me. The good was not good and i noticed that most people around me left most of their meal. The ice cream was very nice. I did not have breakfast. However the food was very nice on the way to Seattle
WestJet
7.2
Good
3,415 reviews
Alaska Airlines
7.9
Good
12,721 reviews

Overall

7.9

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.0

Reviews

1 / 20
6.0
Good

Anonymous,Jul 2026

SEA - LHR

Alaska has a brilliant crew. And the seats are good. As much as i loved my trip from Heathrow to Seattle, i definitely did not feel the same on the return flight. A lot was due to feeling very cramped and unfortunately for me, i had a kicker behind me and a passenger who did not stop moving (but constantly) next to me. The good was not good and i noticed that most people around me left most of their meal. The ice cream was very nice. I did not have breakfast. However the food was very nice on the way to Seattle
Air Canada
7.1
Good
11,398 reviews
Alaska Airlines
7.9
Good
12,721 reviews

Overall

7.9

Boarding

8.1

Entertainment

7.0

Comfort

7.8

Crew

8.5

Food

7.0

Reviews

1 / 20
6.0
Good

Anonymous,Jul 2026

SEA - LHR

Alaska has a brilliant crew. And the seats are good. As much as i loved my trip from Heathrow to Seattle, i definitely did not feel the same on the return flight. A lot was due to feeling very cramped and unfortunately for me, i had a kicker behind me and a passenger who did not stop moving (but constantly) next to me. The good was not good and i noticed that most people around me left most of their meal. The ice cream was very nice. I did not have breakfast. However the food was very nice on the way to Seattle

Related info for your journey

Find useful and relevant information for your journey from Seattle to Ontario. 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 Ontario?

    For a flight from Seattle to Ontario, you will be flying from Seattle/Tacoma Intl. Seattle/Tacoma Intl (SEA) is just 11.4 mi from the center of the city.

  • How long is the flight from Seattle to Region of Ontario?

    Departing from Seattle to Region of Ontario will take you 7h. The distance between Seattle and Region of Ontario is about 2193 mi. When browsing for deals, the options you’ll see will be for both nonstop flights and flights with stops.

  • What are the cheapest airlines to fly from Seattle to Region of Ontario one-way?

    To fly one-way, consider booking your trip with Alaska Airlines, which is currently one of the cheapest options available, starting at $80. WestJet flights start at $83 while deals on Air Canada start at $99 one-way.

  • What are the most popular routes from Seattle to Region of Ontario?

    The most popular route from Seattle to Region of Ontario is Seattle/Tacoma Intl - Toronto Pearson Intl. You may also consider Seattle/Tacoma Intl - Toronto Region of Waterloo Intl or Seattle/Tacoma Intl - Hamilton.

  • What are the most reliable airlines from Seattle to Region of Ontario?

    The top 3 most reliable airlines when flying from Seattle to Region of Ontario are Air Canada (97%), United Airlines (97%) and Brussels Airlines (94%).

  • What are the cheapest flights from Seattle to Region of Ontario?

    Looking for the cheapest flight from Seattle to Region of Ontario? While on average our users pay $941, our data indicates the cheapest price to be $204. The most popular route (Seattle/Tacoma Intl - Toronto Pearson Intl), is priced around $374.

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

    Yes. In addition to deals on Seattle to Ontario flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Seattle to Ontario?

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

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

    Yes. Cheapflights offers flight deals from Seattle to Ontario 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 Region of Ontario?

    Currently, January is the cheapest month in which you can book a flight from Seattle to Region of Ontario (average of $274). Flying from Seattle to Region of Ontario in July is currently the most expensive (average of $600). 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 5 airlines flying from Seattle to Ontario

Discover the top 5 airlines that operate flights from Seattle to Ontario. 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 July 28, 2026.
AirlineCheapestAverageFlexibilityOn-time
Air CanadaCheapest$132Average$506FlexibilityNo cancel feeOn-time67%
DeltaCheapest$142Average$419FlexibilityNo cancel feeOn-timeN/A
WestJetCheapest$228Average$389FlexibilityNo cancel feeOn-time60%
Alaska AirlinesCheapest$250Average$465FlexibilityNo cancel feeOn-time75%
United AirlinesCheapest$277Average$530FlexibilityNo cancel feeOn-time69%

100% Free

Cheapflights is completely free to use, so you can start saving the moment you arrive.

Book with Flexibility

Our users can plan ahead with confidence and find flights with no change fees

Travel Smart

Millions of people come to us for their flight needs every year. We help make travel planning easy by providing useful insights and data-driven graphs that can inform your decisions.