He was born at Crickstown, County Meath, the eldest son of Sir Christopher Bernevall and his wife Matilda Drake. His father was Lord Chief Justice of Ireland. Nicholas was "bred up to the law", and was appointed to the same office as his father in 1457, with a knighthood.
In 1461 he was superseded in favour of Sir Thomas Fitz-Christopher Plunket, but regained office later the same year. He retired about 1463, and was still alive in 1465. Christopher, Nicholas"s eldest son, inherited Crickstown, where the Barnewall family remained for several generations.
In 1623 his descendant Sir Patrick Barnewall was conferred with a baronetcy, which still exists.
Nicholas"s younger brother Robert was created the first Baron Trimleston in 1461.
