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

Return flights

07 Sep - 18 Sep	Aer Lingus	direct
07 Sep - 24 Sep	Delta
10 Sep - 24 Sep	Delta
01 Sep - 11 Sep	Delta
06 Sep - 19 Sep	Delta
30 Sep - 15 Oct	Icelandair
06 Sep - 19 Sep	Aer Lingus	direct
07 Sep - 24 Sep	Aer Lingus	direct
01 Sep - 11 Sep	Aer Lingus	direct
07 Sep - 29 Sep	Icelandair
07 Sep - 12 Sep	Icelandair
10 Sep - 03 Oct	Aer Lingus
17 Sep - 01 Oct	Delta
27 Sep - 04 Oct	Aer Lingus	direct
17 Sep - 01 Oct	Aer Lingus	direct
24 Sep - 04 Oct	Alaska Airlines
26 Sep - 01 Oct	Aer Lingus

Also check the deals for one-way flights from Denver 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 Denver to Dublin in September from 291€

Return flights