The total number of new vehicle registrations for 2019 were down by 6.8%.
The Society of the Irish Motor Industry (SIMI) says total new car registrations finished at 117,100.
Used cars have reached record numbers for a second year: 113,926 used imports were registered - an increase of 13.1%
While 3,444 new electric cars were registered last year, in comparison to 1,233 in 2018.
Diesel accounted for 47%, petrol 41%, hybrid 9%, electric 3% and plug-in hybrid 1%.
Diesel remains the most popular engine type - while hybrid, electric and plug-in hybrid gained market share last year.
Manual transmissions (67%) continue to dominate, with automatic transmissions (33%) gaining in popularity.
Automatic transmissions saw a 22% increase in 2019 as manuals declined by 17%.
The hatchback is Ireland's top selling car body type of 2019 - while grey remains the top-selling colour.
Brian Cooke, SIMI director-general, said: "2019 was a disappointing year for new car sales in Ireland.
"This decline is in part is attributable to the record levels of used imports, which for a second consecutive year exceeded 100,000, having a dampening impact on new car sales.
"2020 marks the start of the new 201 sales period with the Industry firmly focused on January and on the first quarter which is the key selling period.
"The new car market continues to be hugely competitive with generous incentives to buy a new car across all brands and all market segments.
"For consumers looking to change their car this year new or used, SIMI's advice is to shop around and look to buy from your local dealer."