The index closed 11.81 points lower after gaining 3.5 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange decreased by 19.8% to VND20.7 trillion (US$798.6 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 24 tickers fell.
FPT of tech giant FPT Corporation slid 3.2%, BVH of insurance company Bao Viet Holdings went down 2.72%, and VPB of private lender VPBank dropped 2.7%
Four blue chips gained. VRE of retail real estate arm Vincom Retail rose 1.45%, PLX of fuel distributor Petrolimex closed 0.56% higher.
SAB of brewer Sabeco saw a 0.4% growth and VIC of private conglomerate Vingroup was up 0.25%.
Foreign investors were net seller to the tune of VND957 billion, mainly selling VCB of state-owned lender Vietcombank and FPT.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.98%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.04%.