Orphaned at the age of eight, and sent to his late father's family in Scotland at the age of thirteen, Kearsley was educated at Ayr Academy and the University of Edinburgh.

He returned to the United States in 1814, and began studying medicine under Dr. Samuel Powel Griffitts (apprenticeship was a common method of medical education in this period) before enrolling at an institution for his medical education.

[1] Before he went to Philadelphia to practice his profession, he made three voyages to the Far East as ship's surgeon.

[2] From 1841 to 1858, he was professor of the theory and practice of medicine at Jefferson Medical College.

He was also the father of American physician and writer Silas Weir Mitchell (February 15, 1829 – January 4, 1914).