AirHint found the following cheapest return flights from Seoul (GMP) to Ulaanbaatar (UBN) in August 2025 (see full year).

Return flights

29 Aug - 05 Sep	Jeju Air
29 Aug - 02 Sep	T'way Air
31 Aug - 21 Sep	T'way Air
31 Aug - 07 Sep	T'way Air
30 Aug - 06 Sep	T'way Air
29 Aug - 01 Sep	Air China
31 Aug - 06 Sep	Air China
31 Aug - 04 Sep	Air China
29 Aug - 30 Aug	Air China
30 Aug - 01 Sep	Air China
29 Aug - 31 Aug	Air China
30 Aug - 04 Sep	Air China

Also check the deals for one-way flights from Seoul to Ulaanbaatar in August.

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 Seoul to Ulaanbaatar in August from $318

Return flights