But the figure for the period is still a 24% year-on-year drop, according to the Vietnam Automobile Manufacturers Association (VAMA).
In the first nine months sales dropped 29% year-on-year to 209,929 units.
Truong Hai Auto Corporation (Thaco) sold more cars here than any other firm, totaling 67,228 units in the period, down 34% year-on-year.
Toyota followed with 38,490 units, down 40%.
Ford bucked the trend with 71% growth to 26,484 units.
Mitsubishi and Honda rounded out the top five.
Industry insiders said that the rise in September sales came as a batch of new models were released in August and many dealers offered large promotions to boost demand.
Customers also want to take advantage of a reduction in registration fee, which will only last until the end of the year.