The index closed 19.74 points lower after gaining 1.28 points on Friday.
Trading on the Ho Chi Minh Stock Exchange (HoSE) increased by 27% to VND16.40 trillion ($692.42 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 23 tickers dropped.
KDH of real estate firm Khang Dien House and VIC of biggest private conglomerate Vingroup closed at floor price with a 7% drop.
VHM of property giant Vinhomes plunged 6.7%, and VRE of retail real estate arm Vincom Retail fell 6.4%.
Other decliners include PDR of Phat Dat Real Estate Development, down 6.1%, and SSI of leading brokerage SSI Securities Corporation, down 5.4%.
Six blue chips bucked the trend, with NVL of property developer Novaland Group hitting ceiling price with a 6.9% surge.
PLX of fuel distributor Petrolimex gained 2.3%, and BVH of insurance company Bao Viet Holdings went up 1.3%.
Foreign investors were net buyers to the tune of VND329.72 billion, mainly buying DGC of Duc Giang Chemicals Group and SHB of Saigon Hanoi Commercial Bank.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was down 2.98% while the UPCoM-Index at the Unlisted Public Companies Market was down by 0.14%.