Members of the Vietnam Automobile Manufacturers Association (VAMA) reported a rise of nearly 25% in sales to 30,038 units last month.
For the first three months sales were down 22% year-on-year to 70,392 units, with most major brands reporting a steep decline.
Truong Hai Auto Corporation, the top seller, said sales dropped 42% to 20,599 vehicles.
Toyota followed with 13,566 units, down 27%.
Ford, Mitsubishi and Honda rounded off the top five.
Only Ford reported sales growth, in fact a whopping 60%, as it sold 8,668 units.
TC Group, a non-VAMA company that makes Hyundai cars, said quarterly sales fell by 21.1% to 14,736 units.
VinFast, another non-member, sold 1,689 vehicles, all electric, during the quarter.