AirHint found the following cheapest return flights from Zagreb (ZAG) to Bucharest (OTP) in September 2025 (see full year).

Return flights

23 Sep - 27 Sep	Ryanair
23 Sep - 27 Sep	Croatia Airlines	direct
02 Sep - 06 Sep	Croatia Airlines	direct
13 Sep - 16 Sep	Croatia Airlines	direct
19 Sep - 22 Sep	Air Serbia
03 Sep - 06 Sep	Air Serbia
20 Sep - 23 Sep	Croatia Airlines	direct
16 Sep - 21 Sep	Ryanair
01 Sep - 04 Sep	Ryanair
11 Sep - 14 Sep	Ryanair
30 Sep - 04 Oct	Ryanair

Also check the deals for one-way flights from Zagreb to Bucharest 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 Zagreb to Bucharest in September from $144

Return flights