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

Return flights

17 Dec - 07 Jan	Alaska Airlines
17 Dec - 21 Dec	Sun Country Airlines
25 Dec - 30 Dec	Aeromexico	direct
17 Dec - 20 Dec	Sun Country Airlines
17 Dec - 07 Jan	Delta	direct
22 Dec - 01 Jan	Alaska Airlines
22 Dec - 27 Dec	Sun Country Airlines
19 Dec - 21 Dec	Sun Country Airlines
19 Dec - 02 Jan	Sun Country Airlines
20 Dec - 03 Jan	Alaska Airlines
22 Dec - 01 Jan	Aeromexico	direct

Also check the deals for one-way flights from Seattle to Cancun 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 Cancun in December from $643

Return flights