The index closed 13.6 points lower after gaining 19 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange was steady at VND24.2 trillion (US$936 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 23 tickers fell.
GVR of Vietnam Rubber Group plunged 6.9%, followed by BCM of Becamex Investment and Industrial Development with a 6.6% drop.
PLX of fuel distributor Petrolimex lost 3.6% while SSI of brokerage SSI Securities Corporation closed 3.3% lower.
Six blue chips bucked the trend, led by HPG of steelmaker Hoa Phat Group with a 2% gain.
STB of Ho Chi Minh City-based lender Sacombank rose 1.7% and VIC of private conglomerate Vingroup increased by 1.3%.
Foreign investors were net buyers to the tune of VND217 billion.
They mainly net bought HPG and MWG of electronics retail chain Mobile World.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 2.21%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.80%.