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

One-Way flights

25 Aug	United
30 Aug	United
26 Aug	American Airlines
07 Aug	Spirit Airlines
02 Aug	Frontier Airlines
08 Aug	Spirit Airlines
03 Aug	United
28 Aug	Southwest Airlines
06 Aug	Spirit Airlines
10 Aug	Spirit Airlines

Also check the deals for return 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 one-way flights from Seattle to San Juan in August from $188

One-Way flights