He was born at Gibraltar, the son of an army captain and was educated at the grammar schools of Rugby, Sutton Coldfield and Birmingham, and at Christ Church, Oxford, which he entered in 1790. He took holy orders and in 1797 became vicar of Abbots Bromley in Staffordshire. This benefice he held till his death. In 1800 he also became vicar of Kingsbury in Warwickshire. While still at school he had become a regular contributor to the Gentleman's Magazine and had published a volume of Sonnets and Odes.
At Christ Church he devoted much time to the study of French and Italian literature; the fruits of these studies appeared in the notes to his classic translation of Dante. The version of the Inferno was published in 1805 together with the original text.
Soon afterwards Cary moved to London, where he became reader at Berkeley chapel and subsequently lecturer at Chiswick and curate of the Savoy. His version of the whole Divina Commedia did not appear till 1814. It was published at Cary's own expense, as the publisher refused to undertake the risk, owing to the failure incurred over the Inferno. The translation was brought to the notice of Samuel Rogers by Thomas Moore. Rogers made some additions to an article on it by Ugo Foscolo in the Edinburgh Review. This article, and praise bestowed on the work by Coleridge in a lecture at the Royal Institution, led to a general acknowledgment of its merit. Cary's Dante thus gradually took its place among standard works, passing through four editions in the translator's lifetime. It has the great merits of accuracy, idiomatic vigour and readability; it preserves the sincerity and vividness of the original; and, although many rivals have since appeared in the field, it still holds an honourable place. Its blank verse, however, cannot represent the close woven texture and the stately music of the terza rima of the original.
In 1824 Cary published a translation of The Birds of Aristophanes, and, about 1834, of the Odes of Pindar. In 1826 he was appointed assistant-librarian in the British Museum, a post which he held for about eleven years. He resigned because the appointment of keeper of the printed books, which should have been his in the ordinary course of promotion, was refused him when it fell vacant. In 1841 a crown pension of £200 a year, obtained through the efforts of Samuel Rogers, was conferred on him. Cary's Lives of the early French Poets, and Lives of English Poets (from Samuel Johnson to Henry Kirke White), intended as a continuation of Johnson's Lives of the Poets, were published in a collected form in 1846. He died in London and was buried in Westminster Abbey.
A memoir was published by his son, Henry Cary, in 1847.