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

Return flights

09 Dec - 15 Dec	Icelandair	direct
04 Dec - 07 Dec	Icelandair	direct
15 Dec - 10 Jan	Icelandair
09 Dec - 16 Dec	Icelandair
10 Dec - 17 Dec	Southwest Airlines
04 Dec - 09 Dec	Alaska Airlines
15 Dec - 22 Dec	Icelandair
16 Dec - 23 Dec	Icelandair
03 Dec - 10 Dec	Southwest Airlines
04 Dec - 11 Dec	Icelandair
07 Dec - 14 Dec	Southwest Airlines
30 Dec - 06 Jan	Southwest Airlines
22 Dec - 01 Jan	Icelandair	direct
25 Dec - 01 Jan	Alaska Airlines
29 Dec - 05 Jan	Icelandair

Also check the deals for one-way flights from Portland 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 Portland to Keflavik in December from $417

Return flights