This impressive growth figure bucks the industry trend, which saw an overall decline in sales of 14% for Q1 2013 according to figures released by the Society of the Irish Motoring Industry (SIMI).
Cian O'Brien, Director of SEAT Ireland, said: "We are delighted SEAT has seen such a strong start to the year and we remain cautiously optimistic for the remainder of 2013.
"We have registered an impressive 1,205 new cars in the first quarter, which is extremely positive given the challenges facing the industry.
"The all new SEAT Leon launched in February and we have already seen the impact of its arrival with a rise in Leon sales of 109.6% as compared to the same period last year.
"The car has been exceptionally well-received and we plan on capitalising on this encouraging start with continued strong sales and marketing activity, increased dealer support and the introduction of additional Leon models during the year."
SEAT's 2013 market share now stands at 3.05%, up from 1.42% for the same period in 2012.