The index closed 1.60 points lower after gaining 5.51 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange decreased by 4% to VND18.44 trillion ($757.13 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 23 tickers fell.
PLX of fuel distributor Petrolimex dropped 1.8%, followed by VRE of retail real estate arm Vincom Retail with a 1.5% decline.
ACB of Asia Commercial Bank lost 1.4% and BCM of Becamex Investment and Industrial Development closed 1.2% lower.
Seven blue chips gained, led by CTG of state-owned lender VietinBank with a 1.5% rise.
Foreign investors were net sellers to the tune of VND117 billion.
They mainly net bought HPG of steelmaker Hoa Phat Group and VCB of state-owned lender Vietcombank.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.35%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.06%.