The index closed 25.33 points lower after gaining 3.36 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 2% to VND20.64 trillion ($851.22 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw all tickers fell.
MWG of electronics retail chain Mobile World led the decline with a 6.3% plunge, followed by SSI of leading brokerage SSI Securities Corporation, down 6.1%.
HPG of steelmaker Hoa Phat Group dropped 5% and SAB of brewer Sabeco fell 4.9%.
Foreign investors were net seller to the tune of VND439 billion, mainly selling VHM of property giant Vinhomes and VPB of private lender VPBank.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 2.58%, while the UPCoM-Index for the Unlisted Public Companies Market went down 1.29%.