AirHint found the following cheapest return flights from Graz (GRZ) to Kos (KGS) in September 2025 (see full year).

Return flights

17 Sep - 21 Sep	Austrian Airlines
24 Sep - 01 Oct	Eurowings
07 Sep - 14 Sep	Austrian Airlines
17 Sep - 21 Sep	Eurowings	direct
21 Sep - 24 Sep	Eurowings
14 Sep - 21 Sep	Eurowings	direct
23 Sep - 30 Sep	SWISS
24 Sep - 28 Sep	Eurowings
07 Sep - 14 Sep	Eurowings	direct
24 Sep - 28 Sep	Eurowings	direct
21 Sep - 28 Sep	Eurowings	direct
27 Sep - 04 Oct	Austrian Airlines

Also check the deals for one-way flights from Graz to Kos 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 Graz to Kos in September from $183

Return flights