Sales for April are up 28% compared to the same month last year.
So far this year, a total of 57,793 new cars have been sold.
Commenting on the results, Alan Nolan, SIMI Director General, said: "The industry had been closely watching the trend this month, as Easter can have a key impact, with two short weeks, hire-drive business and the potential for car sales to begin to slow down at this time of year.
"The results for April actually confirm that the level of demand has continued at the same rate as earlier months, reflecting increased consumer activity, which augurs well in relation to progress toward economic recovery.
"Commercial vehicle sales are often a better barometer of the domestic economy, and the Heavy Commercial Vehicle market is also showing signs of significant improvement, with sales up 44% year-to-date.
"The increase in Light Commercial Vehicle sales is a sign that small Irish businesses appear more confident about the future.
"While the HGV and LGV figures are off a low base, they do indicate increased activity in the economy."
