AirHint found the following cheapest one-way flights from Seattle (SEA) to Singapore (SIN) in September 2025 (see full year).

One-Way flights

16 Sep	Singapore Airlines	direct
28 Sep	Singapore Airlines	direct
06 Sep	Asiana Airlines
01 Sep	Asiana Airlines
02 Sep	Asiana Airlines
11 Sep	Asiana Airlines
25 Sep	United
05 Sep	China Airlines
02 Sep	Singapore Airlines	direct
11 Sep	Singapore Airlines	direct

Also check the deals for return flights from Seattle to Singapore 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 one-way flights from Seattle to Singapore in September from $305

One-Way flights