The index stayed in the green for most of the day but closed 3.71 points lower due to last-minute selling.
Trading on the Ho Chi Minh Stock Exchange fell by 10.32 percent to VND10.87 trillion ($464.4 million), a six-session low.
The VN-30 basket, comprising the 30 largest capped stocks, saw 22 tickers drop, with VIC of private conglomerate Vingroup losing 2.9 percent to its lowest since March 2020.
BID of lender BIDV dropped 2.7 percent, and HPG of steel giant Hoa Phat ended 2.2 percent lower.
Other losers included CTG of lender VietinBank and SSI of brokerage SSI Securities.
Seven blue chips bucked the downward trend, led by GAS of Petrovietnam Gas with a 3.6 percent gain.
MSN of conglomerate Masan Group surged 2.8 percent, and TCB of lender Techcombank closed 0.7 percent higher.
Foreign investors were net buyers to the tune of VND376.51 billion, focusing mainly on MWG of electronics retailer Mobile World and GAS.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was up 0.26 percent while the UPCoM-Index for the Unlisted Public Companies Market was down 0.31 percent.