The won was quoted at 1,199.1 to the dollar at the conclusion of onshore trade, lowest since March 10, 2016. It closed down 0.4 percent compared to Thursday's close of 1,193.9.
The won, along with other Asian currencies, is under pressure from the prospect of higher U.S. rates and jitters about incoming President Donald Trump's future policies.
South Korean shares changed course later in the session as foreign investors turned into net sellers of local equities.
The Korea Composite Stock Price Index (KOSPI) closed down 0.1 percent at 2,035.73 points.
Offshore investors sold a net 50.6 billion won ($42.21 million) worth of KOSPI shares.