The index closed 2.84 points lower after gaining 4.89 points on Thursday.
Trading on the Ho Chi Minh Stock Exchange (HoSE) increased by 25.73% to VND15.51 trillion ($658.04 million).
Foreign investors have been net-buying non-stop since November 21.
They bought VND265 billion Friday, mainly buying HPG of steelmaker Hoa Phat Group and SSI of leading brokerage SSI Securities Corporation.
The VN-30 basket, comprising the 30 largest capped stocks, saw 19 tickers gain.
HPG led with a 5.4% rise, followed by HDB of HDBank, up 3.3%.
MWG of electronics retail chain Mobile World inched up 1.8%, and NVL of property developer Novaland Group rose 1.7%.
Fourteen blue chips fell, with VRE of retail real estate arm Vincom Retail losing 6.1% and MSN of conglomerate Masan Group falling 4.8%.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was up 0.02% while the UPCoM-Index at the Unlisted Public Companies Market was down by 0.55%.