Dr. Donnelly was born and raised in Stoneham, MA, a suburb of Boston. He attended Stoneham High School and played varsity football, wrestling, and tennis. He received his undergraduate degree from Holy Cross College in Worcester, Massachusetts, majoring in biology. He was a member of the Holy Cross varsity wrestling team. He received his medical degree in 1982 from Cornell University Medical College in New York City. He was captain of Cornell's rugby team.
He was lured to Cincinnati by Dr. McCarren, who ran The University of Cincinnati Family Medicine residency program at that time. He completed his Family Medicine Residency in 1985 and married his bride, Karen, who persuaded him to stay in Ohio. He served four years in the National Health Service Corp in a physician shortage area in rural Ohio and then joined Drs. Bort and McCarren in 1989 on the westside. Named one of Cincy Magazine's 'Top Doctors’ in 2010 and 2011, he has a special interest in high blood pressure, congestive heart failure, and sports medicine.
He is an avid runner, having completed 15 full marathons and 29 Cincinnati Heart Mini Marathons.