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

Return flights

20 Sep - 26 Sep	Aer Lingus
08 Sep - 15 Sep	Air Canada
29 Sep - 13 Oct	Iberia For Level
22 Sep - 30 Sep	SWISS
23 Sep - 29 Sep	SWISS
25 Sep - 30 Sep	SWISS
24 Sep - 01 Oct	SWISS
28 Sep - 07 Oct	SWISS
24 Sep - 29 Sep	SWISS
21 Sep - 01 Oct	Lufthansa
22 Sep - 01 Oct	Lufthansa
28 Sep - 15 Oct	Iberia For Level
15 Sep - 26 Sep	SWISS
08 Sep - 16 Sep	SWISS
09 Sep - 15 Sep	SWISS
20 Sep - 25 Sep	British Airways
30 Sep - 07 Oct	TAP	direct
28 Sep - 15 Oct	TAP	direct
26 Sep - 05 Oct	SWISS
21 Sep - 01 Oct	Virgin Atlantic	direct

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 406€

Return flights