This is the second monthly lowest figure this year behind August with 8,884 units sold, according to Vietnam Automobile Manufacturers Association (VAMA).
In the first nine months, sales rose 5 percent year-on-year, compared to 40 percent in the first half, showing a decline in sales in the third quarter when strict social distancing measures were imposed in Ho Chi Minh City and Hanoi.
Truong Hai Auto Corporation (Thaco) led in sales in the first nine months with 65,764 units sold, up 10 percent year-on-year.
The remaining four companies in the top five saw sales decline.
Toyota came in second with 38,055 units sold, down 7 percent.
It was followed by Mitsubishi, Ford and Honda.
The hatchback VinFast Fadil was the best-selling car in September, followed by the sedan Hyundai Accent and SUV Kia Seltos.