AirHint found the following cheapest return flights from Seattle (SEA) to Dublin (DUB) in September 2025 (see full year).

Return flights

03 Sep - 17 Sep	Air Canada
07 Sep - 17 Sep	Air Canada
10 Sep - 24 Sep	Air Canada
14 Sep - 24 Sep	Air Canada
02 Sep - 12 Sep	Iberia
02 Sep - 16 Sep	Iberia
09 Sep - 23 Sep	Iberia
06 Sep - 17 Sep	Delta
01 Sep - 11 Sep	Air Canada
14 Sep - 24 Sep	Aer Lingus	direct
28 Sep - 05 Oct	Icelandair
27 Sep - 04 Oct	Icelandair
06 Sep - 11 Oct	Scandinavian Airlines
27 Sep - 11 Oct	Icelandair

Also check the deals for one-way flights from Seattle to Dublin 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 Seattle to Dublin in September from 372€

Return flights