AirHint found the following cheapest return flights from Oslo (OSL) to Sofia (SOF) in September 2025 (see full year).

Return flights

07 Sep - 21 Sep	Norwegian	direct
10 Sep - 23 Sep	Lufthansa
28 Sep - 02 Oct	Air Serbia
14 Sep - 28 Sep	Norwegian	direct
04 Sep - 07 Sep	Norwegian	direct
18 Sep - 28 Sep	Norwegian	direct
04 Sep - 21 Sep	Norwegian	direct
18 Sep - 21 Sep	Wizz Air
14 Sep - 21 Sep	Norwegian	direct
18 Sep - 21 Sep	Norwegian	direct
14 Sep - 02 Oct	Norwegian	direct
18 Sep - 02 Oct	Norwegian	direct
28 Sep - 16 Oct	Norwegian	direct
28 Sep - 02 Oct	Norwegian	direct

Also check the deals for one-way flights from Oslo to Sofia 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 Oslo to Sofia in September from $185

Return flights