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

Return flights

10 Dec - 19 Jan	Asiana Airlines	direct
24 Dec - 27 Dec	Korean Air
24 Dec - 27 Dec	Asiana Airlines	direct
23 Dec - 31 Dec	Turkish Airlines
16 Dec - 31 Dec	Turkish Airlines
24 Dec - 06 Jan	Turkish Airlines
21 Dec - 21 Jan	Turkish Airlines
17 Dec - 14 Jan	Korean Air
21 Dec - 21 Jan	Korean Air	direct
26 Dec - 05 Jan	Delta
15 Dec - 02 Jan	Air Canada
11 Dec - 05 Jan	Turkish Airlines
18 Dec - 03 Jan	Turkish Airlines
13 Dec - 03 Jan	Turkish Airlines
16 Dec - 31 Dec	Korean Air	direct

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 742€

Return flights