John Carteret was educated at Westminster School, and at Christ Church, Oxford. Jonathan Swift said that "with a singularity scarce to be justified he carried away more Greek, Latin and philosophy than properly became a person of his rank". Throughout his life Carteret not only showed a keen love of the classics, but a taste for and knowledge of modern languages and literature. He was almost the only English nobleman of his time who spoke German, which allowed him to talk with and gain the trust of King George I, who spoke no English. Walter Harte, the author of the "Life of Gustavus Adolphus", acknowledged the aid which Carteret had given him.