The index closed 5.28 points lower after gaining 6.66 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange decreased by 34% to VND11.72 trillion ($463 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 26 tickers fell.
SSI of leading brokerage SSI Securities Corporation posted the biggest decline at 3%.
POW of electricity producer Petrovietnam Power Corporation fell 2.3% and VRE of retail real estate arm Vincom Retail closed 2.2% lower.
Other losers included CTG of state-owned lender VietinBank (down 2%) and STB of Ho Chi Minh City-based lender Sacombank, (down 1.4%).
Four blue chips bucked the trend, led by BCM of Becamex Investment and Industrial Development with a 3.3% gain.
BVH of insurance company Bao Viet Holdings rose 1.8%, VIC of private conglomerate Vingroup went up 1.7%, and GVR of Vietnam Rubber Group gained 0.9%.
Foreign investors were net sellers to the tune of VND492 billion, mainly selling SSI of leading brokerage SSI Securities Corporation and TLG of office stationary maker Thien Long Group.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.39%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.02%.