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

Return flights

11 Sep - 16 Sep	easyJet
23 Sep - 29 Sep	easyJet
18 Sep - 23 Sep	easyJet
18 Sep - 29 Sep	easyJet
19 Sep - 23 Sep	easyJet
09 Sep - 23 Sep	easyJet
17 Sep - 24 Sep	Volotea
26 Sep - 29 Sep	easyJet
26 Sep - 08 Oct	easyJet
25 Sep - 02 Oct	easyJet
18 Sep - 24 Sep	easyJet
11 Sep - 25 Sep	easyJet
26 Sep - 10 Oct	easyJet
25 Sep - 05 Oct	easyJet
19 Sep - 04 Oct	Ryanair
27 Sep - 02 Oct	Transavia France
27 Sep - 11 Oct	Transavia France
27 Sep - 10 Oct	easyJet
28 Sep - 12 Oct	easyJet
28 Sep - 11 Oct	Ryanair

Also check the deals for one-way flights from Porto to Istanbul 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 Porto to Istanbul in September from 148€

Return flights