Mason Hayes & Curran (MH&C) LLP recorded a 23% rise in revenue to €98 million in 2021.
All areas of the firm grew, with strong growth in corporate, real estate and financial services work.
Energy sector work, particularly renewables, also surged.
The firm acted for AIB in Project Bay, a loan portfolio sale, and in a €400 million loan portfolio sale for Permanent TSB plc.
The built environment market rebounded from the start of 2020 which generated work for specialist planning, construction and real-estate lawyers.
In health and life sciences, there was a high level of activity in the nursing-home sector and also in product regulation.
Lawyer numbers grew by 7% in the year and six new partners joined the firm.
Managing partner Declan Black said: “After a challenging 2020, this performance has returned us to a pre-pandemic growth trajectory, so if external conditions stay favourable we hope to grow considerably again in 2022.”
MH&C also acted for Bauer Media Audio Holding in the acquisition of the entire issued share capital of Communicorp Group Limited from Denis O’Brien.
The firm advised Facebook, Instagram and WhatsApp on the DPC statutory inquiries and acted as privacy counsel for Slack on its $27.7 billion sale to Salesforce.
The financial regulation practice dealt with increased requirements from the Central Bank and the ongoing impact of Brexit.
The firm also advised IAG/Aer Lingus on a $1.8 billion revolving credit facility with a syndicate of banks, and counselled EirGrid on their proposed 700mw subsea 500km electricity interconnector that will link the electricity grids and power markets in Ireland and France.
It acted for Quintain Ireland on its commercial and residential development at Adamstown Station in Dublin.
The business law firm has 95 partners and 540 staff and has offices in London, New York and San Francisco.