Boulter was ordained priest in the Anglican Church and in 1719 became chaplain to King George I. In 1724 he reluctantly accepted appointment as archbishop of Armagh and primate of the Church of Ireland. Appointed lord justice, he became the English government's chief adviser in Ireland.

Boulter based his policies on the conviction that England's interests in Ireland were threatened by the large Roman Catholic majority. Hence, he made the penal laws against Catholics more stringent (1728); Catholics were deprived of the vote and excluded from the legal profession. He also opposed constitutional independence for Irish Protestants but encouraged the establishment of Protestant schools as vehicles to convert the Irish Catholics. At the same time, he sought wherever possible to replace Irishmen with Englishmen in ecclesiastical and political offices. Nevertheless, he made improvements in agriculture and gained some popularity through his generosity to the poor of Dublin.