The index closed 8.67 points lower after gaining 7.37 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 16% to VND14.67 trillion ($604.35 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 28 tickers fell.
VRE of retail real estate arm Vincom Retail plunged 4.7% while VJC of budget airline Vietjet dropped 4.5%.
MSN of conglomerate Masan Group closed 3.8% lower.
Two blue chips gained. GVR of Vietnam Rubber Group rose 0.8%, while VHM of property giant Vinhomes went up 0.2%.
Foreign investors were net sellers to the tune of VND392 billion, mainly selling HPG of steelmaker Hoa Phat Group and VNM of dairy giant Vinamilk.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.39%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.06%.