The index closed 11.77 points lower after losing 6.31 points on Friday.
Trading on the Ho Chi Minh Stock Exchange (HoSE) surged by 27.9% to VND20.56 trillion ($877.69 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 24 tickers dropped.
PDR of Phat Dat Real Estate Development plunged 4.4% to a two-week low.
TPB of private TPBank fell 2.5% to a near four-week low.
VIC of biggest private conglomerate Vingroup dropped 2.2%, and HPG of steelmaker Hoa Phat Group lost 2.1%.
Only three blue chips gained: MWG of electronics retail chain Mobile World went up 2.5%, GAS of state-owned Petrovietnam Gas 2%, and BVH of insurance company Bao Viet Holdings 0.5%.
Foreign investors were net sellers to the tune of VND371.14 billion, mainly selling TLG of office stationary maker Thien Long Group and DGC of Duc Giang Chemicals Group.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was down 1.32% while the UPCoM-Index at the Unlisted Public Companies Market fell 1.41%.