The index closed 5.29 points lower after gaining 10.11 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange decreased by 5% to VND19.70 trillion (US$772 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 21 tickers fell.
VPB of private lender VPBank dropped 2%, followed by MBB of lender MB with a 1.6% decline.
VIC of private conglomerate Vingroup fell 1.5% and CTG of state-owned lender VietinBank closed 1.4% lower.
Seven blue chips gained, with SHB of Saigon Hanoi Commercial Bank increasing 3.1%.
LPB of Fortune Vietnam Bank gained 2% and GAS of state-owned Petrovietnam Gas closed 1.3% lower.
Foreign investors were net seller to the tune of VsND431 billion, mainly selling FPT of tech giant FPT Corporation and SSI of brokerage SSI Securities Corporation.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, rose 0.11%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.14%.