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

Return flights

19 Sep - 29 Sep	Fly Play	direct
23 Sep - 29 Sep	Ryanair
26 Sep - 28 Sep	Ryanair
12 Sep - 19 Sep	Fly Play	direct
19 Sep - 26 Sep	Fly Play	direct
27 Sep - 29 Sep	Ryanair
20 Sep - 28 Sep	Ryanair
23 Sep - 07 Oct	Ryanair
05 Sep - 08 Sep	Fly Play	direct
22 Sep - 29 Sep	Fly Play	direct
25 Sep - 02 Oct	KLM
19 Sep - 24 Sep	Fly Play
26 Sep - 05 Oct	Volotea
26 Sep - 02 Oct	Ryanair
30 Sep - 03 Oct	easyJet
21 Sep - 03 Oct	Ryanair
29 Sep - 03 Oct	Ryanair
28 Sep - 03 Oct	Ryanair
25 Sep - 02 Oct	TAP	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 162€

Return flights