The index closed 8.24 points lower after gaining 0.81 points on August 8.
Trading on the Ho Chi Minh Stock Exchange (HoSE) fell by 6.45% to VND21.71 trillion ($914.16 million).
Foreign investors were net buyers to the tune of VND339.76 billion, mainly buying HPG of steelmaker Hoa Phat Group and MSN of conglomerate Masan Group.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was down 0.08% while the UPCoM-Index at the Unlisted Public Companies Market was up by 0.17%.
