The Straits Times Index reversed some of its gains from last week, ending Monday's trade down by 9.29 points or 0.31% at 2,983.90.
Most of its Asian peers also ended in the red, as markets continue to feel the economic damages of the coronavirus pandemic.
Despite the loss, advancers still outnumbered decliners for the day, 264 to 244, with about 2.37-billion securities worth S$1.58-billion changing hands.
Among the top gainers were Jardine C&C with 5.87% or S$1.22 gain, YZJ Shipbuilding Holdings up by 3.92% or S$0.04 increase, and Keppel Corp which went higher by S$0.01 or 0.18%.
On Wall Street, most US stocks finished the day's trade in negative territory as investors monitored the ongoing US political rows with regards calls to impeach President Donald Trump.
The S&P 500 went down by 25.07 points or 0.66% to 3,799.61, while the Dow Jones Industrial ended lower by 0.29% or 89.28 points at 31,008.69. The NASDAQ also declined by 1.25% or 165.55 points to 13,036.43.
Meanwhile, London's blue-chip index also had a downturn as rising COVID-19 cases in Europe caused jitters on its economic impact.
The FTSE 100 traded lower by 1.09% or 74.78 points at 6,798.48. FTSE 250 also ended down by 1.37% or 288.11 points at 20,776.13.
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