The index closed 13.94 points lower after gaining 5.38 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange decreased by 15.8% to VND29.240 trillion (US$1.18 billion).
The VN-30 basket, comprising the 30 largest capped stocks, saw 26 tickers fell.
GVR of Vietnam Rubber Group slid 4.1% and MSN of conglomerate Masan Group went down 3.8%, followed by CTG of state-owned lender VietinBank with a 2.8% decline.
Only four blue chips gained. TPB of private lender TPBank gained 1.3% and BVH of insurance firm Bao Viet Holdings went up 0.7% while VIC of private conglomerate Vingroup and VPB of lender VPBank both gained 0.5%.
Foreign investors were net seller to the tune of VND539 billion, mainly selling VNM of dairy giant Vinamilk and MSN of Masan Group.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.36%, while the UPCoM-Index for the Unlisted Public Companies Market went up 0.15%.