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

Return flights

19 Sep - 26 Sep	Fly Play	direct
19 Sep - 22 Sep	Fly Play	direct
26 Sep - 03 Oct	Fly Play	direct
26 Sep - 06 Oct	Fly Play	direct
29 Sep - 03 Oct	Fly Play	direct
19 Sep - 29 Sep	Fly Play	direct
26 Sep - 29 Sep	Fly Play	direct
29 Sep - 06 Oct	Fly Play	direct
30 Sep - 09 Oct	Ryanair
15 Sep - 26 Sep	Fly Play	direct
15 Sep - 22 Sep	Fly Play	direct
15 Sep - 21 Sep	Ryanair
12 Sep - 22 Sep	Fly Play	direct
23 Sep - 29 Sep	Ryanair
19 Sep - 21 Sep	Fly Play
30 Sep - 03 Oct	Ryanair
28 Sep - 03 Oct	Ryanair

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 198€

Return flights