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

Return flights

22 Dec - 28 Dec	KLM
25 Dec - 08 Jan	KLM
16 Dec - 06 Jan	KLM
22 Dec - 05 Jan	KLM
06 Dec - 01 Jan	Air France
29 Dec - 04 Jan	KLM
06 Dec - 01 Jan	Turkish Airlines	direct
29 Dec - 04 Jan	Turkish Airlines	direct
25 Dec - 08 Jan	Turkish Airlines	direct
22 Dec - 28 Dec	Turkish Airlines	direct
16 Dec - 06 Jan	Turkish Airlines	direct
22 Dec - 05 Jan	Turkish Airlines	direct

Also check the deals for one-way flights from Seattle to Istanbul 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 Istanbul in December from 650€

Return flights