The index closed 8.4 points lower after gaining 2.62 points on Wednesday.
Trading on the Ho Chi Minh Stock Exchange (HoSE) increased by 8.16% to VND18.60 trillion ($783 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 20 tickers dropped.
VHM of property giant Vinhomes fell 2.9%, followed by STB of Ho Chi Minh City-based lender Sacombank with a 2.7% decline.
PDR of Phat Dat Real Estate Development lost 2.6% and NVL of property developer Novaland Group closed 2% lower.
Eight blue chips gained, led by GVR of Vietnam Rubber Group with a 3% increase.
Foreign investors were net sellers to the tune of VND314.41 billion, mainly selling STB and VCB of state-owned lender Vietcombank.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was down 1.21%while the UPCoM-Index at the Unlisted Public Companies Market was down by 0.37%.