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

Return flights

04 Dec - 07 Dec	SWISS
05 Dec - 07 Dec	Lufthansa
06 Dec - 13 Dec	jetBlue
10 Dec - 19 Dec	Icelandair
23 Dec - 25 Dec	Alaska Airlines
16 Dec - 23 Dec	Frontier Airlines
17 Dec - 22 Dec	Icelandair
17 Dec - 24 Dec	Icelandair
10 Dec - 19 Dec	Icelandair	direct
16 Dec - 23 Dec	Icelandair	direct
27 Dec - 01 Jan	Frontier Airlines
21 Dec - 01 Jan	Frontier Airlines
30 Dec - 05 Jan	Icelandair
30 Dec - 05 Jan	Icelandair	direct
26 Dec - 01 Jan	Frontier Airlines
30 Dec - 03 Jan	Icelandair
21 Dec - 01 Jan	Icelandair	direct
21 Dec - 02 Jan	Frontier Airlines
30 Dec - 03 Jan	Icelandair	direct

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 $642

Return flights