It closed 3.2 points lower after losing 15.6 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, dropped 13% to VND23.86 trillion ($956 million).
The VN30 basket, comprising the 30 largest capped stocks, saw 21 tickers fell.
GVR of Vietnam Rubber Group plunged steepest with a 3.4% decline, followed by MBB of lender MB and TCB of the largest private lender Techcombank, both down 1.7%.
Five blue chips gained, including VCB of state-owned lender Vietcombank with a 2.3% increase and VNM of dairy giant Vinamilk, up 2.2%.
Foreign investors were net buyers after weeks of net selling at the tune of VND484 billion, mainly buying VNM of dairy giant Vinamilk and MWG of electronics retail chain Mobile World.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, dropped 0.62% while the UPCoM-Index for the Unlisted Public Companies Market fell 0.15%.