AirHint found the following cheapest return flights from Seattle (SEA) to Seoul (ICN) in December 2025 (see full year).

Return flights

09 Dec - 24 Dec	Delta	direct
11 Dec - 30 Dec	Delta
15 Dec - 18 Dec	Air Canada
15 Dec - 18 Dec	Asiana Airlines	direct
11 Dec - 30 Dec	Korean Air	direct
15 Dec - 30 Dec	Asiana Airlines	direct
25 Dec - 01 Jan	Air Canada
19 Dec - 09 Jan	Delta	direct
25 Dec - 01 Jan	Korean Air	direct
24 Dec - 04 Jan	United
19 Dec - 10 Jan	Air Canada
18 Dec - 12 Jan	Delta	direct
27 Dec - 03 Jan	Turkish Airlines
15 Dec - 31 Dec	Delta	direct
19 Dec - 10 Jan	Asiana Airlines	direct
24 Dec - 04 Jan	Delta	direct
19 Dec - 03 Jan	China Airlines

Also check the deals for one-way flights from Seattle to Seoul in December.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Seattle to Seoul in December from 754€

Return flights