Leo Sullivan practiced real estate and business law in San Diego for fifty years and served as an an arbitrator with the American Arbitration Association for thirty-five years. Leo graduated from the University of San Francisco and UC Davis Law School and began his career with Gray, Cary, Ames & Frye, now DLA Piper and one of the largest law firms in the world. He founded Sullivan Wertz McDade & Wallace, a mid-size firm which he managed off and on for twenty-five years, and retired as a principal of Sullivan Lawyers. Leo continues to provide non-legal real estate and business consulting services on a limited basis to a few former clients.

Leo was a founder and managing partner of Reidy O'Neil's, a famous but long-defunct Irish Bar and American Grill in the Gaslamp Quarter. He was San Diego chair of the American Ireland Fund and president and Irishman of the Year of the Friendly Sons of St. Patrick.

Leo volunteered as judge advocate of the San Diego Yacht Club, a former home of The America's Cup, and as general counsel to the Top Gun Association, an association of former instructors and students of the Navy's Top Gun school.

Leo is an affiliate member of the Order of St. Augustine, an international order of Catholic priests and brothers. He served on the boards of The St. Augustine Foundation, which supports Augustinian activities throughout the world, Hogar Infantil la Gloria, an orphanage in Tijuana, Villa Merced, a low-income senior housing project in San Ysidro, and St. Augustine High School, his alma mater. Robert Prevost, an Augustinian priest, adopted Leo's name when he was elected pope.

Before law school Leo served as a captain in the Army and was awarded a Bronze Star and Air Medal for service with the First Cavalry Division in Vietnam. He writes historical fiction with military themes, including the acclaimed Columbia Eagle Incident, a novel about the Army’s incursion into Cambodia during the Vietnam War. A third generation San Diegan, Leo lives with his wife Eileen in Point Loma, ten blocks from where his mother was born in 1913 in a house her father built.