AirHint found the following cheapest return flights from Seattle (SEA) to San Juan (SJU) in August 2025 (see full year).

Return flights

29 Aug - 05 Sep	United
24 Aug - 28 Aug	American Airlines
30 Aug - 02 Sep	Alaska Airlines
12 Aug - 27 Aug	American Airlines
28 Aug - 02 Sep	Alaska Airlines
07 Aug - 09 Aug	Spirit Airlines
07 Aug - 11 Aug	Spirit Airlines
28 Aug - 31 Aug	American Airlines
17 Aug - 24 Aug	Alaska Airlines
05 Aug - 13 Aug	American Airlines
06 Aug - 10 Aug	United
07 Aug - 10 Aug	Spirit Airlines
27 Aug - 01 Sep	jetBlue
07 Aug - 08 Aug	Spirit Airlines

Also check the deals for one-way flights from Seattle to San Juan 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 Seattle to San Juan in August from $490

Return flights