The won ended local trade down 0.4 percent at 1,169.6 per dollar. It had gained 1.6 percent over the previous five sessions.
Seoul shares recouped early losses, led by sharp gains in medical supplies stocks on the ex-dividend date.
The Korea Composite Stock Price Index (KOSPI) closed up 0.1 percent at 1,966.31 points in a choppy session.
Foreign investors were net sellers for the 19th straight session, pressing the KOSPI and the won.