It closed 4.76 points lower after losing 13.14 points on Friday.
Trading on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, plunged 19% to VND20.403 trillion ($817.3 million).
The VN30 basket, comprising the 30 largest capped stocks, saw 17 tickers fell.
VRE of retail real estate arm Vincom Retail plummeted 4.5% while STB of Ho Chi Minh City-based lender Sacombank and MWG of electronics retail chain Mobile World both went down 2%.
Nine blue chips gained. HDB of private lender HDBank went up 2.4%, BID of state-owned bank BIDV rose 1.2% and CTG of state-owned lender VietinBank saw a 0.9% growth.
Foreign investors were net sellers to the tune of VND153 billion, mainly selling VHM of property giant Vinhomes and VRE of Vincom Retail.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, dropped 0.67% while the UPCoM-Index for the Unlisted Public Companies Market fell 0.13%.