Cheapest return flights from Seattle to Denver in September from $118

AirHint found the following cheapest return flights from Seattle (SEA) to Denver (DEN) in September 2025 (see full year).

Return flights

24 Sep - 24 Sep Frontier Airlines direct
30 Sep - 05 Oct Frontier Airlines
30 Sep - 02 Oct Frontier Airlines
27 Sep - 30 Sep Frontier Airlines direct
25 Sep - 28 Sep Frontier Airlines
27 Sep - 28 Sep Frontier Airlines
26 Sep - 27 Sep Frontier Airlines
26 Sep - 28 Sep Frontier Airlines
22 Sep - 24 Sep Frontier Airlines
30 Sep - 02 Oct Frontier Airlines direct
20 Sep - 27 Sep Frontier Airlines
20 Sep - 27 Sep Frontier Airlines direct
22 Sep - 24 Sep Frontier Airlines direct
30 Sep - 05 Oct Delta direct
27 Sep - 05 Oct Delta direct

Also check the deals for one-way flights from Seattle to Denver in September.

Skyscanner

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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