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

Return flights

25 Dec - 28 Dec	Air China
15 Dec - 02 Jan	Air China
10 Dec - 17 Dec	Air China
10 Dec - 14 Dec	Air China
31 Dec - 05 Jan	Air China
31 Dec - 04 Jan	Air China
09 Dec - 15 Dec	Air China
20 Dec - 27 Dec	Air China
17 Dec - 20 Dec	Air China
24 Dec - 29 Dec	Air China
05 Dec - 09 Dec	Air China
22 Dec - 29 Dec	Air China
28 Dec - 02 Jan	Air China
19 Dec - 22 Dec	Air China
24 Dec - 04 Jan	Air China
24 Dec - 10 Jan	Air China
29 Dec - 01 Jan	Air China
26 Dec - 02 Jan	Asiana Airlines

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

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 December from $221

Return flights