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

Return flights

13 Aug - 20 Aug	Aer Lingus
25 Aug - 10 Sep	Aer Lingus
24 Aug - 31 Aug	Aer Lingus
22 Aug - 29 Aug	Aer Lingus
17 Aug - 24 Aug	Aer Lingus
28 Aug - 04 Sep	Icelandair
12 Aug - 19 Aug	Air Canada
26 Aug - 02 Sep	Air Canada
30 Aug - 06 Sep	Icelandair
15 Aug - 22 Aug	Aer Lingus
23 Aug - 30 Aug	Icelandair
18 Aug - 25 Aug	Air Canada
21 Aug - 28 Aug	Icelandair
27 Aug - 03 Sep	Aer Lingus
19 Aug - 26 Aug	Icelandair
25 Aug - 01 Sep	Lufthansa
31 Aug - 07 Sep	Lufthansa
29 Aug - 05 Sep	Icelandair
28 Aug - 16 Sep	Icelandair
28 Aug - 18 Sep	Icelandair

Also check the deals for one-way flights from Denver 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 Denver to Lisbon in August from 476€

Return flights