AirHint found the following cheapest return flights from Chicago (ORD) to Seoul (ICN) in September 2025 (see full year).

Return flights

29 Sep - 13 Oct	Cathay Pacific
25 Sep - 12 Oct	Cathay Pacific
16 Sep - 23 Sep	Cathay Pacific
26 Sep - 26 Oct	Cathay Pacific
18 Sep - 25 Sep	Cathay Pacific
30 Sep - 24 Oct	Cathay Pacific
27 Sep - 30 Sep	Spirit Airlines
29 Sep - 13 Oct	Delta	direct
30 Sep - 24 Oct	Delta	direct
26 Sep - 26 Oct	Korean Air	direct
20 Sep - 03 Oct	Delta
25 Sep - 12 Oct	Korean Air	direct
16 Sep - 23 Sep	Korean Air	direct

Also check the deals for one-way flights from Chicago to Seoul 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 Seoul in September from 653€

Return flights