The index was in the green throughout the morning but started to fall after the lunch break and closed with a nearly 5-point drop.
Trading value on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based surged 14 percent to VND26.34 trillion ($1.15 billion). The bourse saw 205 tickers lose and 182 gain.
The VN30 basket, comprising the 30 largest capped stocks, was dominated by red with 18 tickers falling led by KDH of real estate firm Khang Dien House, down 4.4 percent.
SSI of leading brokerage SSI Securities Corporation lost 2.9 percent from its peak, while GVR of Vietnam Rubber Group dropped 2.6 percent.
VIC of biggest private conglomerate Vingroup fell 1.8 percent and brought VN-Index down by 1.8 points, while FPT of IT giant FPT Corporation lost 1.7 percent.
Nine blue chip tickers ended in the green, with TPB of private TPBank gaining 2.8 percent and POW of electricity producer Petrovietnam Power Corporation rising 1.8 percent.
Foreign investors were net sellers to the tune of VND737 billion with strongest pressure on SSI and VCI of Viet Capital Securities.