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

Return flights

06 Dec - 10 Dec	Icelandair
08 Dec - 22 Dec	British Airways
05 Dec - 19 Dec	British Airways
22 Dec - 31 Dec	KLM
16 Dec - 06 Jan	KLM
06 Dec - 10 Dec	Turkish Airlines	direct
08 Dec - 22 Dec	Turkish Airlines	direct
20 Dec - 29 Dec	Icelandair
22 Dec - 31 Dec	Turkish Airlines	direct
20 Dec - 30 Dec	Turkish Airlines	direct
20 Dec - 29 Dec	Turkish Airlines	direct
16 Dec - 06 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 581€

Return flights