The index closed 9.09 points lower after gaining 14.05 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 15% to VND25.430 trillion (US$998.9 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 27 tickers fell.
BVH of insurance company Bao Viet Holdings lost 3.0%, HDB of lender HDBank went down 2.9%, STB of private lender Sacombank closed 2.1% lower.
Only two blue chips gained, which were POW of electricity producer Petrovietnam Power Corporation with a 0.8% growth and GAS of state-owned Petrovietnam Gas, up 0.4%.
Foreign investors were net seller to the tune of VND1657 billion, mainly selling CTG of state-owned lender VietinBank and HPG of steel giant Hoa Phat Group.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.58%, while the UPCoM-Index for the Unlisted Public Companies Market went up 0.27%.