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

Return flights

04 Dec - 11 Dec	Alaska Airlines
03 Dec - 08 Dec	Alaska Airlines
10 Dec - 24 Dec	United
12 Dec - 14 Dec	Frontier Airlines
21 Dec - 23 Dec	Sun Country Airlines
21 Dec - 19 Jan	Sun Country Airlines
23 Dec - 30 Dec	Frontier Airlines
22 Dec - 27 Dec	Air Canada
23 Dec - 28 Dec	Frontier Airlines
23 Dec - 29 Dec	United
22 Dec - 19 Jan	Sun Country Airlines
22 Dec - 29 Dec	Frontier Airlines
25 Dec - 04 Jan	Frontier Airlines
23 Dec - 04 Jan	Frontier Airlines
24 Dec - 03 Jan	Frontier Airlines
26 Dec - 03 Jan	Frontier Airlines

Also check the deals for one-way flights from Seattle to San Jose 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 San Jose in December from $376

Return flights