Born on January 14, 1779, in Calvert County, Maryland. He was the son of Daniel Kent, Sr. (1754–1805) and Anne Weems Wheeler (1761–1823). Joseph Kent received a liberal schooling at Lower Marlboro Academy, and studied medicine. He was admitted to medical practice in Lower Marlborough, Calvert County in 1799 with a Doctor Parran, but ceased relations with Parran after a political disagreement in 1801.

Joseph married first, Eleanor Lee Contee Wallace (1782–1826) on October 30, 1804. Eleanor was born December 9, 1782, in Prince George's County, Maryland. She died August 14, 1826. Eleanor was the daughter Dr. Michael Wallace, Jr., Esq. (1749–1794) and Eleanor Lee Contee (1758–1786). Their daughter, Adelaide MacKubin Kent, would marry Thomas Pratt, another Governor of Maryland and U.S. Senator.

Kent purchased a 300-acre (1.2 km²) slave plantation named "Rosemount" near Bladensburg, Maryland, and settled there around 1807. "Rosemount" is part of the large estate, "Park Hall", owned by the Gantt family in 1735, about which time it was divided and sold. Joseph gave the name "Rosemount". He was passionately fond of roses and the old terraced garden was kept profusely planted with lilies and roses, justifying his choice of the new name he had given his home.

He continued the practice of medicine and also engaged in farming on his estate. In 1807, Dr. Kent removed to the vicinity of Bladensburg and entered the Maryland State Militia as a Surgeon's mate, in the 34th Regiment of the Maryland Militia. In 1809 he was made a full surgeon, but resigned. In the militia, Kent received the rank of a Lieutenant Colonel, and finally as a Colonel of the Cavalry of the 2nd Maryland Militia Cavalry.

Joseph presided at the first public meeting in Washington for the organization of the Chesapeake and Ohio Canal, in which he became a director.

Turning to politics, Joseph was elected to the United States Congress in 1810 taking his seat on March 4, 1811, and served several years until March 3, 1815. Though a Federalist, opposing War with Great Britain, he voted with the Republican party in declaring War. He was a Presidential Elector in 1816, casting his vote for James Monroe (1758–1831). He later broke with the Federalist party and by the time of the next election he was a Democratic-Republican, in which he was elected to another term in the House of Representatives from March 4, 1819, until he resigned on January 6, 1826. In his second tenure in Congress, Kent continued as chairman of the Committee on the District of Columbia.

Joseph was elected Governor of Maryland in 1826. The primary goal of Kent's administration as governor was to work toward internal improvements. He was in support of improving internal transportation, including expanding the Chesapeake and Ohio Canal and the Baltimore and Ohio Railroad. The immense cost of these projects, however, were never fully repudiated until several decades after Kent's administration, and placed the state under immense financial burden for many years aftwards.

Other areas of interest for Kent included prison reform, separating presidential voting into districts, and for increased funding for schools and colleges. He also sought to improve the maintenance of the state's records, "so indispensably necessary to its correct history" as he said.

Joseph married Alice Lee Contee (1803–1868) on July 8, 1828, at "Bromont", near Newburg, Charles Co., Maryland. Alice was born at "Bromont", near Newburg, Charles Co., Maryland. She died August 24, 1868. Alice was the a first cousin of Joseph's first wife, Eleanor Lee Contee Wallace (1782–1826). Alice was the daughter of Capt. Benjamin Contee, Rev., Hon. (1755–1815) and Sarah Russell Lee (1766–1810).

Kent was elected as a Republican (later Whig) to the United States Senate and served from March 4, 1833, until his death at his home, "Rosemount," near Bladensburg. He served as chairman of the Senate Committee on the District of Columbia (Twenty-fourth and Twenty-fifth Congresses). As senator, Kent was opposed to the Bank of the United States, and offered a resolution asking for negotiations with France regarding lower tobacco prices and restricting the importing of tobacco. However, although this resolution passed, it was not widely popular.

Due to ill health, Kent attended only four sessions of the Senate, and died in 1837 as a result of a fall from his horse. He is buried in an unmarked grave at his home of "Rosemount".

• List of United States Congress members who died in office (1790–1899)

• Frank F. White, Jr., The Governors of Maryland 1777-1970 (Annapolis: The Hall of Records Commission, 1970), 87-89.

• United States Congress. "Joseph Kent (id: K000125)". Biographical Directory of the United States Congress.