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

Return flights

29 Sep - 06 Oct	Brussels Airlines
29 Sep - 09 Oct	Brussels Airlines
26 Sep - 05 Oct	Brussels Airlines
29 Sep - 08 Oct	Brussels Airlines
24 Sep - 28 Sep	Icelandair
30 Sep - 09 Oct	Lufthansa
30 Sep - 06 Oct	Lufthansa
26 Sep - 03 Oct	Brussels Airlines
28 Sep - 05 Oct	SWISS
29 Sep - 03 Oct	Aer Lingus
29 Sep - 05 Oct	Lufthansa
23 Sep - 30 Sep	SWISS
17 Sep - 24 Sep	Lufthansa
29 Sep - 30 Sep	Iberia
19 Sep - 25 Sep	Lufthansa
15 Sep - 18 Sep	Aer Lingus
25 Sep - 29 Sep	Lufthansa
16 Sep - 22 Sep	SWISS
22 Sep - 29 Sep	Icelandair
21 Sep - 28 Sep	Iberia

Also check the deals for one-way flights from Boston to Lisbon 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 Lisbon in September from 396€

Return flights