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

Return flights

01 Dec - 08 Dec	Icelandair
04 Dec - 11 Dec	Icelandair
10 Dec - 17 Dec	Icelandair
14 Dec - 23 Dec	Icelandair
07 Dec - 14 Dec	Icelandair
31 Dec - 07 Jan	Icelandair
16 Dec - 23 Dec	Icelandair
12 Dec - 04 Jan	Icelandair
13 Dec - 20 Dec	Icelandair
21 Dec - 28 Dec	Icelandair
26 Dec - 02 Jan	Icelandair

Also check the deals for one-way flights from Seattle to Copenhagen 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 Copenhagen in December from $445

Return flights