Keith Claudius Mitchell was born in the community of Brizan, Saint George's. Mitchell graduated from the University of the West Indies with a Bachelor of Science degree in mathematics and chemistry in 1971. He gained a master's degree from Howard University in 1975 and a doctorate in mathematics and statistics from American University in 1979. He then worked as a statistician at Applied Management Sciences, providing statistical support to the U.S. Energy Information Administration. In 1984, Mitchell gave up his professional activities to return home to Grenada after the U.S. invasion.