The index closed 11.33 points lower after gaining 4.28 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 40% to VND17.81 trillion (US$700 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 28 tickers fell.
SSB of SeABank dropped 4.3%, followed by BCM of Becamex Investment and Industrial Development and TCB of private lender Techcombank, both with a 1.9% decline.
BVH of insurance company Bao Viet Holdings and PLX of fuel distributor Petrolimex were the only two blue chips closing in the green, up 0.4% and 0.3% respectively.
Foreign investors were net sellers to the tune of VND481 billion, mainly selling SSI of brokerage SSI Securities Corporation and VPB of private lender VPBank.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, rose 0.05%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.37%.