The index stayed in the green mostly throughout the day but selling pressure in the last minutes pulled it down by nearly four points.
It has closed in the red in four of five past sessions.
Trading value on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, surged 26 percent to VND27.1 trillion ($1.19 billion), highest since Sept. 6.
The VN30 basket, comprising the 30 largest capped stocks, saw 16 tickers in the red, led by HPG of steelmaker Hoa Phat Group with a 2.8 percent drop.
The ticker is now at its lowest since Oct. 1.
TPB of private TPBank also fell 2.8 percent, its third drop in a row.
TCB of the largest private lender Techcombank fell by 2.7 percent to a two-week low.
Other losers included SSI of leading brokerage SSI Securities Corporation and STB of Ho Chi Minh City-based lender Sacombank, both fell 2.3 percent.
On the other side, BVH of insurance company Bao Viet Holdings shot up 7 percent to a nine-month high as the ticker continued its recovery trend from this year’s bottom in July.
Foreign investors were net sellers for the sixth straight session to the tune of VND1.19 trillion, focusing on VJC of budget airline Vietjet and HPG.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, rose 1.19 percent while the UPCoM-Index for the Unlisted Public Companies Market gained 0.56 percent.