He was the younger son of William Caulfeild, 2nd Viscount Charlemont and the daughter of the Archbishop of Armagh.
In 1710, his regiment was sent to North America, where he took part in Francis Nicholson's successful expedition against Port-Royal, the capital of French Acadia.
In October of that year Nicholson, who was in Boston performing other duties, directed Caulfeild to assume command.
While acting as governor, Caulfeild was involved in several attempts to obtain oaths of allegiance to the British Crown from the Acadian French.
He was unsuccessful in this endeavour, although he did obtain statements of neutrality from them upon the accession of King George I. Caulfeild incurred significant personal debts in maintaining the garrison at Annapolis Royal, and was highly critical of actions by Nicholson that he saw as divisive during Nicholson's brief stay in the province.