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

Return flights

03 Sep - 11 Sep	Air India
11 Sep - 14 Sep	Air India
10 Sep - 13 Sep	Air India
03 Sep - 11 Sep	SriLankan Airlines	direct
11 Sep - 14 Sep	SriLankan Airlines	direct
01 Sep - 30 Oct	Air India
28 Sep - 04 Oct	Air India
29 Sep - 05 Oct	Air India
29 Sep - 05 Oct	SriLankan Airlines	direct

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 $372

Return flights