He was born at Beshellstown, Clonalvy, County Meath to a long established Anglo-Irish family, the main branch of which was settled at Athcarne, near Duleek. The family had a disputed claim to the title Baron Louth. Sir Thomas Bathe, an earlier Chief Baron, belonged to the same family, as did John Bathe, Chief Justice of the Irish Common Pleas. James entered Middle Temple in 1522 and was Master of the Revels in 1524.
In the early stages of his career he was a firm adherent of Gerald FitzGerald, 9th Earl of Kildare. In 1525 while in England he took the opportunity to present the Crown with a book on the reformation of the administration of Ireland. This step aroused the hostility of the increasingly powerful Cowley family: Robert Cowley, the head of he family, warned Cardinal Wolsey that the book was in fact an effort to persuade Henry VIII that there was no solution to Ireland's problems but the return to power of Kildare, who was then in temporary disgrace. Cowley wrote contemptuously that Bathe "knows as much about Ireland as I do about Italy", and should be "touched (i.e. rebuked) for his presumption.
He narrowly escaped being implicated in the rebellion of Silken Thomas, as, in addition to his former loyalty to Thomas's father the 9th Earl of Kildare, he was a friend of several of the rebels, and had recently married the daughter of John Burnell of Balgriffin, one of the ringleaders of the rebellion. Robert Cowley and his son Walter Cowley continued their attacks on him, arguing that he was unfit to be appointed to even a minor administrative post, for "his conduct is disagreeable to the duty of a true subject" (presumably this was an attack on his loyalty during the recent rebellion).
Fortunately for Bathe, he had some influential friends, including Thomas St. Lawrence, the Attorney General for Ireland, through whom he gained the confidence of the Lord Deputy, Leonard Grey, and was sent by him to report to Thomas Cromwell on the state of Irish government. He survived Grey's downfall in 1540 and played a considerable role in the Dissolution of the Monasteries. He outwardly conformed to the Church of Ireland but is said to have remained a member of the Roman Catholic Church in private.
He was appointed the Irish Chief Baron in 1540 and held office under each successive Tudor monarch until his death in 1570, being commended for his good service to the Crown, despite some complaints about his slowness in collecting revenue. In his last years his health and faculties began to fail, and there were numerous complaints about his incapacity for office. Sir Henry Sidney, the Lord Deputy of Ireland wrote to Elizabeth I caustically in 1567 about the state of the Exchequer of Ireland : "God knoweth how your revenues and finances are there ordered".
He married firstly Marjorie Ballard of Drogheda, who died sometime after 1530, and secondly Elizabeth Burnell, daughter of John Burnell of Balgriffin, and widow of Robert Barnewall of Drimnagh Castle. By his second wife he had at least two children:John Bathe of Drumcondra Castle, Attorney General for Ireland and Chancellor of the Irish Exchequer (died 1586), who had eight children including-
William Bathe, the well-known Jesuit writer and musician.
Jane Bathe, who married Sir Lucas Dillon, who succeeded his father-in-law as Chief Baron; they were parents of-
James Dillon, 1st Earl of Roscommon.
James Bathe became a very substantial landowner in Dublin: he acquired Drimnagh Castle through marriage and began the building of another castle at Drumcondra, which his son completed, as well as acquiring lands north of the River Liffey. LIke other landowners of the time he was not always scrupulous in his means of acquisition: in 1551 he and his wife received a royal pardon for "intruding" on lands which should have passed to Edward Barnewall, her son by her first husband. James's son John added greatly to the family's landholding, but most of it was lost over the next two generations.