New figures from the Central Statistics Office show that the number of new cars licensed in August rose by 37.7% to 6,201 on the same time last year.
This compared to a gain of over 50% in July, when the new 142 registration plate came into effect.
However, used cars licensed for the first time fell by 3.3% to 4,278 last month.
The CSO said that a total of 82,518 new cars were licensed in the year to the end of August, up 30.3% compared to the same time last year.
Today's figures also show that the number of new goods vehicles licensed last month jumped by 52.3% to 1,550.
The most popular new car sold last month was Volkswagen, followed by Ford, Toyota and Nissan.
