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

Return flights

27 Sep - 02 Oct	Icelandair
27 Sep - 05 Oct	Icelandair
20 Sep - 25 Sep	Icelandair
24 Sep - 05 Oct	Icelandair
13 Sep - 05 Oct	Icelandair
24 Sep - 08 Oct	SWISS
29 Sep - 07 Oct	SWISS
22 Sep - 15 Oct	SWISS
29 Sep - 06 Oct	SWISS
30 Sep - 07 Oct	Delta
30 Sep - 08 Oct	Delta
13 Sep - 21 Sep	Icelandair
22 Sep - 27 Sep	Air Canada
26 Sep - 30 Sep	Delta
23 Sep - 30 Sep	Delta
19 Sep - 26 Sep	Air Canada
20 Sep - 28 Sep	Icelandair
24 Sep - 28 Sep	Icelandair
15 Sep - 17 Sep	SWISS
17 Sep - 24 Sep	Air France

Also check the deals for one-way flights from Newark 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 Newark to Lisbon in September from 359€

Return flights