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

Return flights

15 Sep - 24 Sep	Asiana Airlines
07 Sep - 25 Sep	Asiana Airlines
16 Sep - 23 Sep	Asiana Airlines
22 Sep - 03 Oct	Asiana Airlines
25 Sep - 30 Sep	Asiana Airlines
04 Sep - 17 Sep	Delta	direct
16 Sep - 23 Sep	Delta	direct
15 Sep - 24 Sep	Delta	direct
04 Sep - 18 Sep	Delta	direct
25 Sep - 30 Sep	Delta	direct
01 Sep - 25 Sep	Delta	direct
22 Sep - 03 Oct	Delta	direct
22 Sep - 04 Oct	Delta	direct

Also check the deals for one-way flights from Seattle to Taipei 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 Seattle to Taipei in September from 527€

Return flights