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

Return flights

29 Dec - 12 Jan	Aer Lingus
08 Dec - 15 Dec	United
05 Dec - 22 Dec	Lufthansa
23 Dec - 30 Jan	British Airways
09 Dec - 16 Dec	Iberia
11 Dec - 23 Dec	Alaska Airlines
11 Dec - 18 Dec	Iberia
14 Dec - 23 Dec	Alaska Airlines
10 Dec - 17 Dec	Iberia
28 Dec - 12 Jan	Alaska Airlines
16 Dec - 25 Dec	Finnair
15 Dec - 18 Dec	Air France
26 Dec - 06 Jan	Hawaiian Airlines
28 Dec - 05 Jan	Aer Lingus
29 Dec - 06 Jan	Turkish Airlines
14 Dec - 21 Dec	Iberia
31 Dec - 07 Jan	United
23 Dec - 01 Jan	Alaska Airlines
19 Dec - 01 Jan	Frontier Airlines
19 Dec - 03 Jan	Hawaiian Airlines

Also check the deals for one-way flights from Seattle to Madrid 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 Madrid in December from $673

Return flights