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

Return flights

16 Sep - 02 Oct	Iberia Express
16 Sep - 24 Sep	Iberia Express
24 Sep - 01 Oct	Ryanair
16 Sep - 01 Oct	Iberia Express
16 Sep - 23 Sep	Iberia Express
13 Sep - 23 Sep	Iberia Express
14 Sep - 24 Sep	Iberia Express
27 Sep - 01 Oct	Ryanair
16 Sep - 25 Sep	Iberia Express
25 Sep - 02 Oct	Wizz Air Malta
27 Sep - 02 Oct	Ryanair
17 Sep - 24 Sep	Ryanair
13 Sep - 25 Sep	Iberia Express
14 Sep - 20 Sep	Iberia Express
14 Sep - 17 Sep	Fly Play	direct
16 Sep - 29 Sep	Iberia Express
25 Sep - 05 Oct	Wizz Air Malta
26 Sep - 08 Oct	Ryanair
29 Sep - 05 Oct	Ryanair
26 Sep - 06 Oct	Ryanair

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 $211

Return flights