The rise in share was driven by sales increasing 7pc year-on-year in the first quarter of this year.
The Seat Arona, performed especially well, accounting for 29pc of overall sales during the three months, a massive increase of 69pc on the same period in 2018.
Niall Phillips, brand director at Seat Ireland, said: “We have really hit the ground running in 2019 and as we reflect on very strong sales for Q1, we can confidently point to the significant impact the brand is having in the Irish market as we become more and more relevant for Irish consumers.”
Seat Ireland is a subsidiary of Spanish group Seat.
The company has responsibility for a 24-strong dealer network in Ireland.
Founded in 1950, Seat was sold by the Spanish government to Volkswagen in 1986.