The index closed 4.38 points lower after gaining 9.47 points on Thursday.
Trading on the Ho Chi Minh Stock Exchange (HoSE) increased by 30% to VND11.95 trillion ($509.23 million).
The VN-30 basket, comprising the 30 largest capped stocks, saw 14 tickers dropped.
MSN of conglomerate Masan Group fell 3.7%, and GVR of Vietnam Rubber Group lost 3.4%.
PDR of Phat Dat Real Estate Development dropped 2.6%, and SSI of leading brokerage SSI Securities Corporation went down 2.1%.
Twelve blue chips gained, with SAB of brewer Sabeco rising 3.7% and VIB of Vietnam International Commercial Bank increasing by 2.5%.
Foreign investors were net buyers to the tune of VND348.97 billion, mainly buying HPG of steelmaker Hoa Phat Group and VRE of retail real estate arm Vincom Retail.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was down 1.15% while the UPCoM-Index at the Unlisted Public Companies Market was down by 0.10%.