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

Return flights

28 Sep - 06 Oct	Air Canada
10 Sep - 17 Sep	Air Canada
15 Sep - 22 Sep	Air Canada
14 Sep - 25 Sep	Iberia
07 Sep - 17 Sep	Air Canada
24 Sep - 30 Sep	SWISS
21 Sep - 11 Oct	Air Canada
02 Sep - 19 Sep	United
21 Sep - 28 Sep	Iberia
23 Sep - 18 Oct	British Airways
22 Sep - 28 Sep	British Airways
18 Sep - 30 Sep	Iberia
14 Sep - 04 Oct	Air Canada
09 Sep - 04 Oct	Air Canada
25 Sep - 29 Sep	SWISS
20 Sep - 11 Oct	SWISS
19 Sep - 10 Oct	British Airways
18 Sep - 11 Oct	Iberia
27 Sep - 18 Oct	Iberia
28 Sep - 06 Oct	TAP	direct

Also check the deals for one-way flights from Boston to Porto 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 Boston to Porto in September from $401

Return flights