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

Return flights

26 Aug - 02 Sep	SWISS
27 Aug - 03 Sep	Air Canada
31 Aug - 07 Sep	Lufthansa
18 Aug - 13 Sep	United
17 Aug - 06 Sep	Iberia
19 Aug - 13 Sep	United
28 Aug - 04 Sep	Lufthansa
16 Aug - 06 Sep	United
20 Aug - 13 Sep	United
31 Aug - 20 Sep	Lufthansa
17 Aug - 25 Aug	SWISS
25 Aug - 27 Aug	SWISS
17 Aug - 19 Aug	SWISS
19 Aug - 22 Aug	United
20 Aug - 21 Aug	SWISS
25 Aug - 27 Aug	TAP	direct
17 Aug - 25 Aug	TAP	direct

Also check the deals for one-way flights from Boston to Porto in August.

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 August from 374€

Return flights