The index closed 24.34 points lower after gaining 3.03 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 65% to VND24.334 trillion ($1 billion).
The VN-30 basket, comprising the 30 largest capped stocks, saw all tickers fell.
VIC of private conglomerate Vingroup plunged 6.4%, followed by VHM of property giant Vinhomes, down 5.3%, and VRE of retail real estate arm Vincom Retail, down 4.4%.
Foreign investors were net sellers to the tune of VND748 billion, mainly selling VHM and MWG of electronics retail chain Mobile World.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 1.32%, while the UPCoM-Index for the Unlisted Public Companies Market went down 1.28%.