The Central Statistics Office said 2,272 new cars were licensed in the month, a drop of 47.9%.
Though the drop is steep, it is not as big as the 73% and 64.5% falls recorded in July and August respectively.
For the first nine months of the year, the new car figure was 51,414, a drop of 63.8% from the 141,930 recorded in the same period last year.
The CSO figures show that almost 60% of the new cars licensed last month were diesel, with just under 39% petrol.
Ford led the way with 292, followed by Toyota (257) and Volkswagen (256).
