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

Return flights

14 Sep - 23 Sep	KLM
01 Sep - 10 Sep	Air France
08 Sep - 17 Sep	Air France
01 Sep - 09 Sep	Air France
08 Sep - 18 Sep	Delta
09 Sep - 16 Sep	Delta
21 Sep - 26 Sep	Porter Airlines (Canada) Ltd
14 Sep - 19 Sep	Frontier Airlines
08 Sep - 15 Sep	Air France
27 Sep - 04 Oct	Porter Airlines (Canada) Ltd
30 Sep - 16 Oct	KLM
08 Sep - 14 Sep	Porter Airlines (Canada) Ltd
26 Sep - 07 Oct	Porter Airlines (Canada) Ltd
30 Sep - 06 Oct	Air France
25 Sep - 03 Oct	Frontier Airlines

Also check the deals for one-way flights from Chicago 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 Chicago to Dublin in September from 515€

Return flights