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

Return flights

07 Jul - 24 Jul	Icelandair	direct
08 Jul - 15 Jul	Icelandair	direct
10 Jul - 17 Jul	Icelandair	direct
12 Jul - 19 Jul	Icelandair	direct
14 Jul - 21 Jul	Icelandair	direct
15 Jul - 22 Jul	Icelandair	direct
16 Jul - 23 Jul	Icelandair	direct
17 Jul - 24 Jul	Icelandair	direct
18 Jul - 25 Jul	Icelandair	direct
24 Jul - 31 Jul	Icelandair	direct
24 Jul - 17 Aug	Icelandair	direct
28 Jul - 11 Aug	Icelandair	direct
25 Jul - 01 Aug	Icelandair	direct

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

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 July from 407€

Return flights