The index closed 9.82 points lower after losing 1.75 points on Friday.
Trading on the Ho Chi Minh Stock Exchange (HoSE) fell by 36% to VND14.32 trillion ($608.71 million).
Foreign investors were net sellers to the tune of VND107.32 billion, mainly selling NVL of property developer Novaland Group and VNM of dairy giant Vinamilk.
The VN-30 basket, comprising the 30 largest capped stocks, saw 18 tickers fall.
NVL plunged 6%, followed by PDR of Phat Dat Real Estate Development with a 4.2% fall.
VCB of state-owned lender Vietcombank declined by 3.1% and MSN of conglomerate Masan Group lost 2.7%.
Ten blue chips gained, led by SAB of brewer Sabeco with a 1.2% rise.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was down 0.84% while the UPCoM-Index at the Unlisted Public Companies Market was down by 0.08%.