AirHint found the following cheapest return flights from Istanbul (IST) to Helsinki (HEL) in September 2025 (see full year).

Return flights

12 Sep - 18 Sep	Pegasus Airlines
04 Sep - 13 Sep	Pegasus Airlines	direct
23 Sep - 28 Sep	Pegasus Airlines
10 Sep - 16 Sep	Pegasus Airlines	direct
10 Sep - 17 Sep	Pegasus Airlines	direct
12 Sep - 15 Sep	Pegasus Airlines
03 Sep - 05 Sep	Pegasus Airlines
02 Sep - 09 Sep	Pegasus Airlines
01 Sep - 06 Sep	Pegasus Airlines
03 Sep - 09 Sep	Pegasus Airlines	direct

Also check the deals for one-way flights from Istanbul to Helsinki 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 Istanbul to Helsinki in September from 140€

Return flights