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

Return flights

19 Aug - 27 Aug	Air Canada
19 Aug - 28 Aug	Air Canada
25 Aug - 02 Sep	Brussels Airlines
13 Aug - 10 Sep	Turkish Airlines
19 Aug - 26 Aug	Icelandair
23 Aug - 01 Sep	Air Canada
18 Aug - 06 Sep	Scandinavian Airlines
11 Aug - 20 Aug	Aer Lingus
24 Aug - 30 Aug	TAP	direct
31 Aug - 08 Sep	Turkish Airlines
19 Aug - 27 Aug	TAP	direct
19 Aug - 28 Aug	TAP	direct
24 Aug - 31 Aug	Air Canada
13 Aug - 18 Aug	Air Canada
23 Aug - 30 Aug	TAP	direct
31 Aug - 20 Sep	Turkish Airlines
27 Aug - 02 Sep	Aer Lingus
25 Aug - 01 Sep	British Airways
31 Aug - 07 Sep	Air Canada
25 Aug - 02 Sep	TAP	direct

Also check the deals for one-way flights from Washington to Lisbon 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 Washington to Lisbon in August from $473

Return flights