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

Return flights

29 Aug - 07 Sep	Fly Play
28 Aug - 31 Aug	KLM
22 Aug - 25 Aug	Fly Play	direct
27 Aug - 03 Sep	Air Europa
30 Aug - 07 Sep	TAP
29 Aug - 04 Sep	Fly Play
25 Aug - 01 Sep	Fly Play
31 Aug - 05 Sep	Air Europa
30 Aug - 06 Sep	TAP
25 Aug - 01 Sep	Fly Play	direct
31 Aug - 07 Sep	TAP
25 Aug - 28 Aug	Fly Play
26 Aug - 30 Aug	Ryanair
28 Aug - 18 Sep	Vueling Airlines
22 Aug - 26 Aug	Ryanair
15 Aug - 18 Aug	Fly Play	direct
13 Aug - 19 Aug	TAP
23 Aug - 30 Aug	TAP
18 Aug - 21 Aug	TAP
21 Aug - 28 Aug	SWISS

Also check the deals for one-way flights from Lisbon to Keflavik in August.

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 August from 298€

Return flights