The index closed 8.38 points lower after gaining 13.50 points on Tuesday.
Trading on the Ho Chi Minh Stock Exchange (HoSE) fell by 12.40 percent to VND9.77 trillion ($412.34 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 26 tickers dropped.
KDH of real estate firm Khang Dien House plunged 5.8% to a near 16-month low.
MWG of electronics retail chain Mobile World dipped 2.4%, and POW of electricity producer Petrovietnam Power Corporation fell 1.8%.
Other losers included POW of electricity producer Petrovietnam Power Corporation, STB of Ho Chi Minh City-based lender Sacombank and CTG of state-owned lender VietinBank.
Three blue chips gained, led by VNM of dairy giant Vinamilk with a 1.5% rise, followed by BVH of insurance company Bao Viet Holdings and SAB of brewer Sabeco.
Foreign investors were net sellers to the tune of VND122.05 billion, mainly selling VHM of real estate giant Vinhomes and VND of brokerage VNDirect.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was down 0.68% while the UPCoM-Index at the Unlisted Public Companies Market was down by 0.32%.