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

Return flights

30 Sep - 08 Oct	easyJet
16 Sep - 24 Sep	easyJet
09 Sep - 24 Sep	easyJet
09 Sep - 17 Sep	easyJet
10 Sep - 17 Sep	easyJet
24 Sep - 01 Oct	Ryanair
18 Sep - 24 Sep	Wizz Air Malta
17 Sep - 24 Sep	Ryanair
09 Sep - 15 Sep	Ryanair
18 Sep - 23 Sep	Wizz Air Malta
14 Sep - 19 Sep	Fly Play	direct
30 Sep - 05 Oct	easyJet
27 Sep - 03 Oct	Ryanair
26 Sep - 01 Oct	Ryanair
10 Sep - 15 Sep	Ryanair
26 Sep - 03 Oct	easyJet
24 Sep - 03 Oct	Wizz Air Malta
28 Sep - 10 Oct	Fly Play	direct
08 Sep - 10 Oct	Iberia
28 Sep - 03 Oct	Fly Play	direct

Also check the deals for one-way flights from Madrid to Keflavik in September.

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 Madrid to Keflavik in September from $179

Return flights