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

Return flights

10 Sep - 17 Sep	Air Canada
30 Sep - 14 Oct	Air Canada
12 Sep - 19 Sep	Air Canada
08 Sep - 20 Sep	Air Canada
09 Sep - 17 Sep	Air Canada
26 Sep - 05 Oct	Air Canada
15 Sep - 17 Sep	Air Canada
18 Sep - 25 Sep	Air Canada
30 Sep - 16 Oct	Air Canada
11 Sep - 18 Sep	Air Canada
22 Sep - 29 Sep	Cathay Pacific
11 Sep - 17 Sep	Cathay Pacific
18 Sep - 23 Sep	Cathay Pacific
30 Sep - 31 Oct	Air Canada
19 Sep - 04 Oct	Air Canada
26 Sep - 17 Oct	Cathay Pacific

Also check the deals for one-way flights from Washington 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 Washington to Seoul in September from $1004

Return flights