Mason Hayes & Curran has moved to LLP status since 25 May.
It becomes the largest law firm in Ireland to switch to limited liability partnership under LSRA regulations which became operational in October.
The Barrow Street, Dublin 4, business law firm has 95 partners and reported revenue of €85 million in 2019.
The LSRA began accepting applications for authorisation as an LLP last November following the commencement of chapter 3 of part 8 of the Legal Services Regulation Act 2015.
The Law Society director general Ken Murphy said last year that he hoped "that all partners and firms will avail of this significant advantage, long fought for".