The index remained in the red throughout the day and closed 4.67 points lower, after gaining over 40 points in the last five sessions.
Trading on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, fell by nearly 20 percent to the two-week low of VND21.76 trillion ($952 million).
The VN30 basket, comprising the 30 largest capped stocks, saw 19 tickers losing with VNM of dairy giant Vinamilk dropping 2.2 percent, ending its six-session winning streak.
BID of state-owned lender BIDV fell 2.1 percent, and VPB of private lender VPBank closed in the red for the first time in five sessions, losing 1.8 percent.
Other losers included SSI of leading brokerage SSI Securities, down 1.6 percent, and KDH of housing developer Khang Dien and CTG of VietinBank, both down 1.5 percent.
Eleven blue chips gained, led by GAS of Petrovietnam Gas with a 1.7 percent rise to its near two-week high.
NVL of real estate giant Novaland climbed 1.4 percent to its fresh near three-month high. It gained more than 9 percent over the last four sessions.
Foreign investors were net sellers to the tune of VND277 billion, focusing on FLC of property developer FLC Group and HPG of steelmaker Hoa Phat.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, lost 0.56 percent while the UPCoM-Index for the Unlisted Public Companies Market rose 0.03 percent.