The index closed 0.47 points lower after gaining 8.71 points in the previous session.
Trading on the Ho Chi Minh Stock Exchange increased by 31% to VND20.03 trillion ($822.92 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 20 tickers fell.
Sixteen blue chips fell. GVR of Vietnam Rubber Group dropped 2.3% and TPB of private TPBank closed 2% lower.
VIB of Vietnam International Commercial Bank fell 1.9% and VPB of private lender VPBank declined by 1.8%.
Ten blue chips rose. GVR of Vietnam Rubber Group led with a 2.7% rise, followed by MWG of electronics retail chain Mobile World, up 2.6%.
HDB of HDBank rose 2.5% and FPT of IT giant FPT Corporation closed 2.1% higher.
Foreign investors were net sellers to the tune of VND209 billion, mainly selling VNM of dairy giant Vinamilk and SHS of Saigon – Hanoi Securities.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, fell 0.01%, while the UPCoM-Index for the Unlisted Public Companies Market went up 0.41%.