The index closed 0.59 points lower after gaining 9 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 27% to VND16.73 trillion ($681.74 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 17 tickers fell.
VHM of property giant Vinhomes dropped 1.8%, followed by SHB of Saigon Hanoi Commercial Bank, down 1.6%.
TPB of private TPBank fell 1.3% and MSN of conglomerate Masan Group closed 1.2% lower.
Nine blue chips gained, led by MWG of electronics retail chain Mobile World with a 1.4% rise.
Foreign investors were net buyers to the tune of VND143 billion, mainly buying MWG and HPG of steelmaker Hoa Phat Group.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, was unchanged while the UPCoM-Index for the Unlisted Public Companies Market went down 0.08%.