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

Return flights

13 Sep - 02 Oct	Air Canada
12 Sep - 19 Sep	Icelandair
06 Sep - 13 Sep	Icelandair
13 Sep - 02 Oct	Aer Lingus	direct
17 Sep - 25 Sep	Scandinavian Airlines
10 Sep - 21 Sep	SWISS
27 Sep - 11 Oct	Icelandair
27 Sep - 04 Oct	Icelandair
18 Sep - 24 Sep	Aer Lingus	direct
22 Sep - 29 Sep	Aer Lingus	direct
17 Sep - 25 Sep	Aer Lingus	direct
01 Sep - 29 Sep	Aer Lingus
18 Sep - 04 Oct	Air Canada
27 Sep - 11 Oct	Aer Lingus	direct

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 $437

Return flights