The index closed 37.15 points lower after gaining 1.10 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 83% to VND21.065 trillion ($863.29 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw all tickers fell.
GVR of Vietnam Rubber Group hit the floor with a 6.9% dive, followed by SSI of leading brokerage SSI Securities Corporation, down 5.9%.
MWG of electronics retail chain Mobile World dropped 5.6% and BID of state-owned lender BIDV closed 5.5% lower.
Foreign investors were net seller to the tune of VND154 billion, mainly selling CTG of state-owned lender VietinBank and VPB of private lender VPBank.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, dropped 4.24% while the UPCoM-Index for the Unlisted Public Companies Market fell 2.27%.