AirHint found the following cheapest return flights from Portland (PDX) to San Francisco (SFO) in September 2025 (see full year).

Return flights

13 Sep - 16 Sep	United	direct
27 Sep - 27 Sep	United	direct
17 Sep - 22 Sep	United	direct
23 Sep - 30 Sep	United	direct
20 Sep - 22 Sep	United	direct
18 Sep - 22 Sep	United	direct
27 Sep - 29 Sep	United	direct
13 Sep - 15 Sep	United	direct
06 Sep - 09 Sep	United	direct
25 Sep - 29 Sep	United	direct
30 Sep - 01 Oct	United	direct
28 Sep - 05 Oct	United	direct

Also check the deals for one-way flights from Portland to San Francisco 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 Portland to San Francisco in September from 91€

Return flights