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

Return flights

30 Sep - 15 Oct	Icelandair
16 Sep - 23 Sep	Icelandair
10 Sep - 24 Sep	SWISS
17 Sep - 24 Sep	Icelandair
09 Sep - 24 Sep	Icelandair
04 Sep - 18 Sep	Icelandair
07 Sep - 24 Sep	Icelandair
06 Sep - 19 Sep	Icelandair
03 Sep - 17 Sep	Air Canada
30 Sep - 08 Oct	Icelandair
23 Sep - 01 Oct	Icelandair
27 Sep - 05 Oct	Icelandair
29 Sep - 07 Oct	Icelandair
17 Sep - 10 Oct	Icelandair
17 Sep - 08 Oct	Icelandair
03 Sep - 11 Sep	KLM
15 Sep - 25 Sep	Icelandair
10 Sep - 03 Oct	British Airways
24 Sep - 02 Oct	Iberia
28 Sep - 06 Oct	British Airways

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 $362

Return flights