AirHint found the following cheapest return flights from Colombo (CMB) to Kathmandu (KTM) in September 2025 (see full year).

Return flights

17 Sep - 21 Sep	Air India
18 Sep - 30 Sep	Air India
20 Sep - 27 Sep	Air India
21 Sep - 28 Sep	Air India
22 Sep - 29 Sep	SriLankan Airlines
22 Sep - 08 Oct	SriLankan Airlines
17 Sep - 22 Sep	SriLankan Airlines
24 Sep - 02 Oct	SriLankan Airlines
17 Sep - 24 Sep	SriLankan Airlines
17 Sep - 21 Sep	SriLankan Airlines	direct
17 Sep - 24 Sep	SriLankan Airlines	direct
17 Sep - 22 Sep	SriLankan Airlines	direct
19 Sep - 05 Oct	flydubai

Also check the deals for one-way flights from Colombo to Kathmandu 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 Colombo to Kathmandu in September from 366€

Return flights