Dr. James Leonard was raised in Morris, Illinois and received his B.A. in Psychology from the University of Illinois, Champaign-Urbana in 1977. Dr. Leonard was awarded an M.D. degree in 1981 from the University of Illinois in Chicago. He completed his residency training in family medicine at MacNeal Hospital in Berwyn, Illinois. In 1984 he and his family relocated to Champaign-Urbana to join the Carle Clinic Association. Dr. Leonard practiced family medicine and founded Carle's drug and alcohol program. Dr. Leonard was recognized in 1998 with the Illinois Society of Addictive Medicine Career Achievement Award.

Dr. Leonard also served as the head of Carle's Sports medicine program and in 1996 was a physician at the Olympic Games in Atlanta. He has served in many clinical leadership roles in the Carle organization including Associate Medical Director and Vice President of Medical Affairs. In July of 2000, Dr. Leonard was selected as CEO and President of the Carle Foundation and continues to serve in that position.