The index closed 4.94 points lower after gaining 10.46 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 52% to VND27.45 trillion ($101 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 14 tickers fell.
GVR of Vietnam Rubber Group dropped 2.9%, followed by GAS of state-owned Petrovietnam Gas, down 2.4%.
SSI of leading brokerage SSI Securities Corporation declined by 2.2% and PLX of fuel distributor Petrolimex closed 2.1% lower.
Thirteen blue chips gained, led by MSN of conglomerate Masan Group, up 2.3%.
Foreign investors were net sellers to the tune of VND816 billion, mainly selling VHM of property giant Vinhomes and HPG of steelmaker Hoa Phat Group.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.77%, while the UPCoM-Index for the Unlisted Public Companies Market went down 0.79%.