AirHint found the following cheapest return flights from Seattle (SEA) to Lisbon (LIS) in August 2026 (see full year).

Return flights

21 Aug - 29 Aug	Scandinavian Airlines
22 Aug - 29 Aug	Scandinavian Airlines
12 Aug - 19 Aug	Lufthansa
11 Aug - 19 Aug	Lufthansa
19 Aug - 26 Aug	Air Canada
18 Aug - 25 Aug	Air Canada
17 Aug - 25 Aug	Air Canada
18 Aug - 26 Aug	Air Canada
19 Aug - 27 Aug	Air Canada
24 Aug - 01 Sep	Scandinavian Airlines
11 Aug - 18 Aug	Air Canada
31 Aug - 29 Sep	Air Canada
28 Aug - 30 Sep	United

Also check the deals for one-way flights from Seattle 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 Seattle to Lisbon in August from 509€

Return flights