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

Return flights

09 Dec - 20 Dec	Icelandair
09 Dec - 20 Dec	Turkish Airlines	direct
10 Dec - 21 Dec	Lufthansa
11 Dec - 18 Dec	Lufthansa
11 Dec - 18 Dec	Turkish Airlines	direct
16 Dec - 30 Dec	Lufthansa
13 Dec - 27 Dec	Delta
13 Dec - 27 Dec	Turkish Airlines	direct
16 Dec - 30 Dec	Turkish Airlines	direct

Also check the deals for one-way flights from Denver 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 Denver to Istanbul in December from 756€

Return flights