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

Return flights

02 Dec - 15 Dec	easyJet
06 Dec - 12 Dec	SWISS
30 Dec - 11 Jan	easyJet
09 Dec - 17 Dec	easyJet
02 Dec - 14 Dec	easyJet
09 Dec - 11 Dec	easyJet
10 Dec - 14 Jan	easyJet
09 Dec - 18 Dec	easyJet
05 Dec - 08 Dec	easyJet
06 Dec - 13 Dec	easyJet
04 Dec - 07 Dec	easyJet
09 Dec - 21 Dec	easyJet
30 Dec - 07 Jan	easyJet
29 Dec - 07 Jan	easyJet
29 Dec - 02 Jan	easyJet
20 Dec - 04 Jan	Transavia France
25 Dec - 01 Jan	Wizz Air
19 Dec - 07 Jan	easyJet
27 Dec - 05 Jan	easyJet
26 Dec - 05 Jan	Wizz Air

Also check the deals for one-way flights from Keflavik to Madrid 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 Keflavik to Madrid in December from $175

Return flights