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

Return flights

08 Sep - 23 Sep	Air Canada
15 Sep - 22 Sep	Air Canada
16 Sep - 23 Sep	jetBlue
29 Sep - 06 Oct	jetBlue
08 Sep - 15 Sep	jetBlue
11 Sep - 18 Sep	jetBlue
17 Sep - 24 Sep	British Airways
18 Sep - 25 Sep	jetBlue
24 Sep - 01 Oct	Air Canada
09 Sep - 13 Sep	Air Canada
03 Sep - 09 Sep	Air Canada
30 Sep - 14 Oct	Delta
12 Sep - 19 Sep	jetBlue
24 Sep - 07 Oct	Delta
25 Sep - 02 Oct	KLM
02 Sep - 29 Oct	TAP

Also check the deals for one-way flights from Washington 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 Washington to Lisbon in September from $491

Return flights