The index stayed in the red throughout the day and closed over six points lower, continuing its sideways trend which began mid-February.
"As the global financial markets see strong fluctuations, it is unavoidable for Vietnamese investors sentiment to be negatively impacted," a report by Vietcombank Securities said.
It expects the benchmark to stay in the 1,480-1,510 range for the next few weeks.
Trading value on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, surged 6 percent to VND31.44 trillion ($1.37 billion), highest in seven sessions.
The VN30 basket, comprising the 30 largest capped stocks, saw 22 tickers in the red, led by TPB of private lender TPBank with a 4.3 percent fall to a six-week low.
VJC of budget airline Vietjet lost 3.7 percent to a three-week low, while SAB of brewer Sabeco fell 3.4 percent to a near four-week low.
Other losers included ACB of Asia Commercial Bank, down 3.1 percent, VRE of retail real estate arm Vincom Retail, down 2.5 percent, and BID of state-owned lender BIDV, down 2.4 percent.
Seven blue chip tickers bucked the trend, with GAS of state-owned Petrovietnam Gas gaining 5.6 percent, and PLX of fuel distributor Petrolimex rising 3.6 percent.
Foreign investors were net sellers to the tune of VND1.47 billion, highest in nearly seven weeks, with focus on NLG of real estate developer Nam Long Investment Corp and VHM of real estate giant Vinhomes.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, rose 0.5 percent while the UPCoM-Index for the Unlisted Public Companies Market lost 0.06 percent.