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

Return flights

31 Jul - 04 Aug	Frontier Airlines
30 Jul - 06 Aug	Frontier Airlines
28 Jul - 02 Aug	Frontier Airlines
31 Jul - 02 Aug	Frontier Airlines
31 Jul - 14 Aug	United
29 Jul - 12 Aug	United	direct
30 Jul - 13 Aug	United	direct
30 Jul - 06 Aug	United	direct
28 Jul - 11 Aug	United
28 Jul - 11 Aug	United	direct

Also check the deals for one-way flights from Denver to San Juan in July.

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 July from 228€

Return flights