AirHint found the following cheapest return flights from Washington (DCA) to San Juan (SJU) in September 2025 (see full year).

Return flights

15 Sep - 19 Sep	United
25 Sep - 28 Sep	Southwest Airlines
20 Sep - 27 Sep	United
08 Sep - 12 Sep	United
23 Sep - 27 Sep	United
09 Sep - 23 Sep	United
16 Sep - 30 Sep	United
23 Sep - 07 Oct	United
24 Sep - 08 Oct	United
30 Sep - 14 Oct	United
17 Sep - 01 Oct	United
20 Sep - 04 Oct	United
21 Sep - 05 Oct	United
22 Sep - 01 Oct	Southwest Airlines
01 Sep - 01 Oct	United
27 Sep - 11 Oct	United
15 Sep - 29 Sep	United
24 Sep - 29 Sep	Southwest Airlines
08 Sep - 22 Sep	United
19 Sep - 03 Oct	United

Also check the deals for one-way flights from Washington to San Juan in September.

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 Washington to San Juan in September from 140€

Return flights