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

Return flights

23 Dec - 26 Dec	Icelandair	direct
21 Dec - 28 Dec	Frontier Airlines
24 Dec - 28 Dec	Icelandair
22 Dec - 29 Dec	Frontier Airlines
24 Dec - 28 Dec	Icelandair	direct
22 Dec - 24 Dec	Southwest Airlines
20 Dec - 24 Dec	Icelandair
24 Dec - 01 Jan	Icelandair	direct
23 Dec - 30 Dec	Icelandair
21 Dec - 28 Dec	Icelandair	direct
27 Dec - 01 Jan	Icelandair
22 Dec - 29 Dec	Icelandair	direct
26 Dec - 01 Jan	Lufthansa
30 Dec - 03 Jan	Frontier Airlines

Also check the deals for one-way flights from Denver to Keflavik 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 Keflavik in December from 658€

Return flights