The index closed nearly 6 points higher after losing 3 points on Tuesday.
Trading on the Ho Chi Minh Stock Exchange (HoSE) increased by 6.1 percent to VND10.02 trillion ($428 million).
Foreign investors were net buyers to the tune of VND618 billion, higher than the last three sessions combined.
They mainly bought KDC of food producer KIDO Group and MWG of electronics retail chain Mobile World.
The VN-30 basket, comprising the 30 largest capped stocks, saw 18 tickers gain.
BVH of insurance company Bao Viet Holdings led with a 5.1 percent surge.
CTG of state-owned lender VietinBank followed with a 1.7 percent rise.
Other gainers included GVR of Vietnam Rubber Group, VCB of state-owned lender Vietcombank and HDB of HDBank, up by 1.3-1.5 percent.
Seven blue chips fell, with HPG of steelmaker Hoa Phat Group losing 1.8 percent to the lowest in five weeks after posting a 60 percent plunge in profit in the second quarter.
Other losers included MWG of electronics retail chain Mobile World, MBB of lender MB and NVL of real estate developer Novaland Group, losing by 0.3-1.4 percent.
The HNX-Index at the Hanoi Stock Exchange, where mid and small caps list, was up 0.58 percent while the UPCoM-Index at the Unlisted Public Companies Market was up by 0.52 percent.