The index closed 9.37 points lower after gaining 12.88 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange decreased by 11% to VND12.59 trillion ($517.26 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 26 tickers fell.
SSB of SeABank dropped 3.6%, followed by VRE of retail real estate arm Vincom Retail, down 3.5%.
MSN of conglomerate Masan Group closed 3.1% lower and VHM of property giant Vinhomes declined 2.4%.
MWG of electronics retail chain Mobile World bucked the trend with a 0.4% rise, and HPG of steelmaker Hoa Phat Group went up 0.2%.
Foreign investors were net sellers to the tune of VND264 billion, mainly selling MWG and VRE of retail real estate arm Vincom Retail.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.59%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.52%.