AirHint found the following cheapest return flights from Seattle (SEA) to Keflavik (KEF) in June 2025 (see full year).

Return flights

29 Jun - 10 Jul	Icelandair	direct
26 Jun - 10 Jul	Icelandair	direct
29 Jun - 27 Jul	Icelandair	direct
29 Jun - 09 Jul	Icelandair	direct
21 Jun - 27 Jun	Icelandair	direct
15 Jun - 20 Jun	KLM
17 Jun - 23 Jun	KLM
23 Jun - 04 Jul	Delta
23 Jun - 30 Jun	Delta
24 Jun - 30 Jun	Delta
22 Jun - 30 Jun	Delta
23 Jun - 28 Jun	Icelandair	direct
20 Jun - 25 Jun	Delta
20 Jun - 01 Jul	Delta
24 Jun - 30 Jun	Icelandair	direct
22 Jun - 30 Jun	Icelandair	direct
29 Jun - 08 Jul	Icelandair	direct
30 Jun - 08 Jul	Icelandair	direct
23 Jun - 04 Jul	Icelandair	direct
23 Jun - 01 Jul	Icelandair	direct

Also check the deals for one-way flights from Seattle to Keflavik in June.

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 Seattle to Keflavik in June from $480

Return flights