The local currency was quoted at 1,091.2 against the dollar at the end of onshore trade, compared with 1,090.9 at the end of the Seoul session on Friday.
"Nobody's willing to carry big positions ahead of the US elections. There is still some dollar supply from exporters, but it's not as big a rush as there had been last week," a local bank dealer said.
Investors also remained cautious about potential intervention by local foreign exchange authorities should the won test the 1,090 resistance level again, dealers said.
Finance Bahk Jae-wan told Reuters on the sidelines of a meeting of G20 ministers and central bankers in Mexico that the won's recent appreciation has been faster than expected and that the government is watching the market closely.
Dealers suspect that local authorities have intervened several times to slow the won's gains in recent weeks. Bahk reiterated that the government is concerned about excessive volatility in the won's value as opposed to targeting a specific level.
The benchmark Korea Composite Stock Price Index ended down 0.6 percent at 1,908.22. Foreigners were net sellers of 66.9 billion won ($61.3 million) worth of local shares on Monday.
Bonds fell on profit-taking as foreign investors began trimming their positions. December futures on three-year treasury bonds ended down 0.07 point at 106.17.
Yields on the benchmark five-year treasury bonds and three-year treasury bonds each rose 2 basis points from Friday's close.