Born in Calvert County, Maryland to Daniel and Anne Wheeler Kent, Joseph Kent received a liberal schooling 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. Kent purchased a 300-acre estate named "Rose Mount" near Bladensburg, Maryland, and settled there around 1807. He continued the practice of medicine and also engaged in farming on his estate. He entered the Maryland State Militia as a Surgeon's mate in 1807, and was later made a full surgeon. In the militia, Kent received the rank of a Lieutenant Colonel, and finally as a Colonel of the Cavalry.

Kent was elected as a Federalist to the Twelfth and Thirteenth Congresses, and served from March 4, 1811 until March 3, 1815. In Congress, he served as chairman of the Committee on the District of Columbia (Thirteenth Congress), and, although he was against war, he voted in favor of war against Great Britain, resulting in the War of 1812. Kent was elected to the Sixteenth and to the three succeeding Congresses and served from March 4, 1819, to January 6, 1826, when he resigned, having been elected Governor of Maryland. Kent continued as chairman on the Committee on the District of Columbia (Sixteenth through Nineteenth Congresses).

The primary goal of Kent's administration as governor was to work towards internal improvement. 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 burdon 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.

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, ”Rose Mount,” 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 "Rose Mount".