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

Return flights

27 Sep - 01 Oct	easyJet
20 Sep - 01 Oct	easyJet
05 Sep - 15 Sep	Fly Play	direct
19 Sep - 29 Sep	Fly Play	direct
30 Sep - 07 Oct	easyJet
19 Sep - 24 Sep	Vueling Airlines
29 Sep - 06 Oct	Vueling Airlines
12 Sep - 15 Sep	Fly Play	direct
23 Sep - 30 Sep	easyJet
10 Sep - 16 Sep	TAP
24 Sep - 29 Sep	Vueling Airlines
18 Sep - 23 Sep	Ryanair
29 Sep - 03 Oct	TAP
19 Sep - 26 Sep	Fly Play	direct
26 Sep - 06 Oct	TAP
25 Sep - 30 Sep	Ryanair
10 Sep - 09 Oct	TAP
27 Sep - 07 Oct	easyJet
28 Sep - 03 Oct	Vueling Airlines
26 Sep - 06 Oct	Fly Play	direct

Also check the deals for one-way flights from Lisbon 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 Lisbon to Keflavik in September from 220€

Return flights