AirHint found the following cheapest one-way flights from Seattle (SEA) to Denver (DEN) in October 2025 (see full year).

One-Way flights

15 Oct	Frontier Airlines	direct
12 Oct	Frontier Airlines	direct
17 Oct	Frontier Airlines	direct
18 Oct	Frontier Airlines	direct
26 Oct	Frontier Airlines	direct
10 Oct	Frontier Airlines	direct
22 Oct	Frontier Airlines	direct
21 Oct	Alaska Airlines	direct
01 Oct	Frontier Airlines	direct
11 Oct	Frontier Airlines	direct

Also check the deals for return flights from Seattle to Denver in October.

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 one-way flights from Seattle to Denver in October from $22

One-Way flights