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

Return flights

30 Sep - 13 Oct	SWISS
30 Sep - 13 Oct	Aer Lingus	direct
27 Sep - 07 Oct	United	direct
28 Sep - 06 Oct	United	direct
29 Sep - 12 Oct	SWISS
23 Sep - 18 Oct	SWISS
24 Sep - 18 Oct	SWISS
21 Sep - 17 Oct	Scandinavian Airlines
26 Sep - 28 Sep	Air Canada
25 Sep - 30 Sep	Frontier Airlines
25 Sep - 18 Oct	Frontier Airlines
26 Sep - 18 Oct	SWISS
18 Sep - 24 Sep	Frontier Airlines
20 Sep - 27 Sep	Frontier Airlines
17 Sep - 26 Sep	Turkish Airlines
21 Sep - 27 Sep	Turkish Airlines
19 Sep - 22 Sep	TAP
26 Sep - 28 Sep	United	direct
17 Sep - 26 Sep	Aer Lingus	direct
18 Sep - 24 Sep	Aer Lingus	direct

Also check the deals for one-way flights from Washington 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 Washington to Dublin in September from 536€

Return flights