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

Return flights

13 Dec - 21 Dec	Scandinavian Airlines
03 Dec - 10 Dec	TAP	direct
08 Dec - 15 Dec	TAP	direct
13 Dec - 20 Dec	Scandinavian Airlines
17 Dec - 25 Dec	Air Canada
18 Dec - 25 Dec	United
13 Dec - 21 Dec	TAP	direct
13 Dec - 20 Dec	TAP	direct
17 Dec - 25 Dec	TAP	direct
20 Dec - 25 Dec	Scandinavian Airlines
28 Dec - 04 Jan	United
29 Dec - 03 Jan	TAP
29 Dec - 03 Jan	TAP	direct
30 Dec - 04 Jan	TAP	direct

Also check the deals for one-way flights from Washington 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 Washington to Lisbon in December from $579

Return flights