The index fell 39.8 points after dropping 19.7 points on September 22, the third consecutive losing session.
Trading on the Ho Chi Minh Stock Exchange (HoSE) slumped 27% to 23.49 trillion VND (963.49 million USD).
The VN30 basket saw 26 tickers fell.
The HNX-Index for stocks on the Hanoi Stock Exchange dropped 4.79% while the UPCoM-Index for the Unlisted Public Companies Market fell 2.27%.