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

Return flights

18 Sep - 20 Sep	Air Canada
16 Sep - 19 Sep	Air Canada
27 Sep - 05 Oct	Air Canada
16 Sep - 23 Sep	Air Canada
17 Sep - 24 Sep	Air Canada
18 Sep - 25 Sep	Cathay Pacific
26 Sep - 05 Oct	Air Canada
19 Sep - 26 Sep	Frontier Airlines
17 Sep - 24 Sep	Korean Air	direct
18 Sep - 25 Sep	Delta	direct
16 Sep - 23 Sep	Delta	direct
18 Sep - 20 Sep	Delta	direct
27 Sep - 05 Oct	Delta	direct
26 Sep - 04 Oct	Delta	direct
26 Sep - 05 Oct	Delta	direct
26 Sep - 03 Oct	Delta

Also check the deals for one-way flights from Boston 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 Boston to Seoul in September from 722€

Return flights