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

Return flights

31 Dec - 08 Jan	Icelandair
30 Dec - 23 Jan	Iberia
29 Dec - 17 Jan	Aer Lingus
06 Dec - 12 Dec	Aer Lingus
08 Dec - 12 Dec	Aer Lingus
06 Dec - 09 Dec	Aer Lingus
05 Dec - 12 Dec	Air Canada
30 Dec - 18 Jan	Delta
04 Dec - 10 Dec	Aer Lingus
30 Dec - 12 Jan	British Airways
30 Dec - 08 Jan	Iberia
04 Dec - 13 Dec	Air Canada
04 Dec - 11 Dec	Aer Lingus
08 Dec - 16 Dec	Aer Lingus
04 Dec - 09 Dec	Aer Lingus
01 Dec - 08 Dec	SWISS
13 Dec - 08 Jan	Icelandair
28 Dec - 12 Jan	Azores Airlines
15 Dec - 09 Jan	Azores Airlines
27 Dec - 16 Jan	Iberia

Also check the deals for one-way flights from Boston to Lisbon in December.

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 December from $421

Return flights