The index closed 0.26 points lower after gaining 4.59 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 31% to VND19.33 trillion ($795 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 13 tickers gained and 13 fell.
The top gainers included TPB of private TPBank, up 2.1%, followed by MSN of conglomerate Masan Group, up 1.2%.
SAB of brewer Sabeco fell by 1%.
Foreign investors were net buyers to the tune of VND113 billion. They mainly net bought VNM of dairy giant Vinamilk and HDG of construction firm Ha Do Group.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.29%, while the UPCoM-Index for the Unlisted Public Companies Market went up 0.19%.