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

Return flights

03 Dec - 07 Dec	Lufthansa
03 Dec - 10 Dec	Icelandair	direct
09 Dec - 16 Dec	Icelandair
11 Dec - 18 Dec	Frontier Airlines
02 Dec - 05 Dec	Icelandair	direct
10 Dec - 17 Dec	Icelandair
08 Dec - 15 Dec	Icelandair
11 Dec - 14 Dec	Icelandair
14 Dec - 21 Dec	Icelandair
16 Dec - 23 Dec	Icelandair
31 Dec - 07 Jan	Frontier Airlines
30 Dec - 06 Jan	Icelandair
27 Dec - 01 Jan	Frontier Airlines
29 Dec - 05 Jan	Icelandair	direct
30 Dec - 06 Jan	Icelandair	direct
24 Dec - 05 Jan	Icelandair
25 Dec - 01 Jan	Frontier Airlines
26 Dec - 01 Jan	Frontier Airlines
28 Dec - 04 Jan	Frontier Airlines
30 Dec - 03 Jan	Icelandair

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 540€

Return flights