The index closed 15.34 points lower after gaining 3.96 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 70% to VND23.31 trillion ($954.15 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 27 tickers fell.
SHB of Saigon Hanoi Commercial Bank plunged the steepest at 5.7%, followed by VRE of retail real estate arm Vincom Retail, down 4.1%.
VCB of state-owned lender Vietcombank dropped 2.7% and MSN of conglomerate Masan Group declined by 2.6%.
Three blue chips gained. SSI of leading brokerage SSI Securities Corporation went up 0.7%, while FPT of IT giant FPT Corporation and VNM of dairy giant Vinamilk both inched up 0.1%.
Foreign investors were net buyers to the tune of VND120 billion, mainly buying AIC of Vietnam National Aviation Insurance and SSI of leading brokerage SSI Securities Corporation.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.64%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.19%.