AirHint found the following cheapest return flights from Denver (DEN) to San Juan (SJU) in October 2025 (see full year).

Return flights

04 Oct - 09 Oct	Frontier Airlines
18 Oct - 27 Oct	Frontier Airlines
15 Oct - 19 Oct	Frontier Airlines
16 Oct - 20 Oct	Frontier Airlines
14 Oct - 23 Oct	Frontier Airlines
09 Oct - 13 Oct	Frontier Airlines
22 Oct - 05 Nov	United
07 Oct - 21 Oct	United
28 Oct - 11 Nov	United
24 Oct - 07 Nov	United
01 Oct - 15 Oct	United	direct
08 Oct - 22 Oct	United	direct
09 Oct - 23 Oct	United	direct
27 Oct - 10 Nov	United	direct
29 Oct - 12 Nov	United	direct
23 Oct - 06 Nov	United
19 Oct - 02 Nov	United
18 Oct - 01 Nov	United	direct
26 Oct - 09 Nov	United
21 Oct - 04 Nov	United	direct

Also check the deals for one-way flights from Denver to San Juan 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 return flights from Denver to San Juan in October from 171€

Return flights