The index closed 3.15 points lower after gaining 7.01 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange decreased by 33% to VND12.700 trillion (US$502 million), its lowest since May 31.
The VN-30 basket, comprising the 30 largest capped stocks, saw 17 tickers fell.
VHM of property giant Vinhomes saw the biggest fall of 3.7%, SSI of brokerage SSI Securities Corporation followed with a 1.3% drop while PLX of fuel distributor Petrolimex slipped 1.2%.
Eight blue chips gained. STB of Ho Chi Minh City-based lender Sacombank went up 2.2%, VIB of Vietnam International Commercial Bank rose by 1.3%, and TCB of private lender Techcombank closed 1.1% higher.
Foreign investors were net seller to the tune of VND141 billion, mainly selling MBB of MB Bank and VHM.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, rose 0.14%, while the UPCoM-Index for the Unlisted Public Companies Market went up 0.08%.
Globally, European and Asian shares slipped on Wednesday on uncertainty surrounding a closely contested U.S. election, Reuters reported.
With tepid appetite for risk, the Euro STOXX 600 fell 0.6% ahead of a slew of key economic data.
Still, Wall Street futures , ticked higher, buoyed by a solid result from Google-parent Alphabet, which reported quarterly revenue that beat estimates.
Earlier in Asia, MSCI's broadest index of Asia-Pacific shares outside Japan fell to a one-month trough and were last down 0.7%, tracking a decline in Chinese assets.