AirHint found the following cheapest return flights from Taipei (TPE) to Seattle (SEA) in September 2025 (see full year).

Return flights

11 Sep - 28 Sep	Delta	direct
09 Sep - 21 Sep	Delta	direct
04 Sep - 08 Sep	Delta	direct
08 Sep - 20 Sep	Delta	direct
18 Sep - 26 Sep	Delta	direct
14 Sep - 29 Sep	Delta	direct
16 Sep - 29 Sep	Delta	direct
08 Sep - 22 Sep	Delta	direct
05 Sep - 08 Sep	Delta	direct
02 Sep - 17 Sep	Delta	direct
18 Sep - 06 Oct	Delta	direct
17 Sep - 06 Oct	Delta	direct
15 Sep - 01 Oct	Delta	direct
11 Sep - 01 Oct	Delta	direct
11 Sep - 02 Oct	Delta	direct
18 Sep - 03 Oct	Delta	direct
18 Sep - 08 Oct	Delta	direct
07 Sep - 21 Oct	Delta	direct
24 Sep - 14 Oct	Delta	direct
16 Sep - 06 Oct	Delta	direct

Also check the deals for one-way flights from Taipei to Seattle 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 Taipei to Seattle in September from $634

Return flights