Kent was the son of Moss Kent, a Lawyer from Dutchess County, New York and the first Surrogate of Rensselaer County, New York. He graduated from Yale College in 1781, having helped establish the Phi Beta Kappa Society there in 1780, and began to practice law at Poughkeepsie, New York in 1785 as an attorney, and in 1787 at the bar. In 1791 and 1792-93 Kent was a member from Dutchess County of the New York State Assembly. In 1793, he removed to New York City, where he was appointed a master in chancery for the city.

Kent was the first professor of law in Columbia College in 1793-98 and again served in the Assembly in 1796-97. In 1797, he was appointed Recorder of New York City and in 1798, a justice of the New York Supreme Court, in 1804 Chief Justice, and in 1814 Chancellor of New York. Kent was also elected a member of the American Antiquarian Society in 1814. In 1821 he was a member of the New York State Constitutional Convention where he unsuccessfully opposed the raising of the property qualification for African American voters. Two years later, Chancellor Kent reached the constitutional age limit and retired from his office, but was re-elected to his former chair. He lived in retirement in Summit, New Jersey between 1837 and 1847 in a simple four-roomed cottage (the original cottage today has been incorporated into a large mansion at 50 Kent Place Boulevard in Summit NJ) which he referred to as 'my Summit Lodge', a name that has been offered as the derivation for the city's name.

Kent married Elizabeth Bailey, and they had four children: Elizabeth (died in infancy), Elizabeth, Mary, and william Kent (1802–1861) who was a circuit judge and ran for Lieutenant Governor of New York with Washington Hunt in 1852.

Kent has been long remembered for his Commentaries on American Law (four volumes, published 1826-1830), highly respected in England and America. The Commentaries treated state, federal and international law, and the law of personal rights and of property, and went through six editions in Kent's lifetime.