The index closed 6 points lower after gaining 7 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange (HoSE) decreased by 3.6% to VND23.204 trillion (US$935.8 million).
The VN30 basket, comprising the 30 largest capped stocks, saw 22 tickers fell.
MSN of conglomerate Masan Group went down 2.4% while SHB of private lender SHB and SSI of brokerage SSI Securities Corporation both fell 1.7%.
Seven blue chips gained. VIB of lender VIB grew 1.4%, VRE of retail real estate arm Vincom Retail went up 0.8% and ACB of Asia Commercial Joint Stock Bank increased by 0.5%.
Foreign investors were net sellers to the tune of VND795 billion, mainly selling MSN of conglomerate Masan Group and VND of securities brokerage VNDirect.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.55% while the UPCoM-Index for the Unlisted Public Companies Market rose 0.09%.