Michael O'Neill is being inducted to the Lacrosse Hall of Fame as "a truly great player." In 1974, O'Neill received high school All-America honors as a player for Massapequa High School in New York. At John Hopkins University, he was a three-time First-Team All-American in 1976, 1977 and 1978. He received Second-Team All-America honors in 1975. He was a member of the Johns Hopkins national championship team of 1978. He received the outstanding Division I attackman award in 1977 and 1978. In 1978, he also received the Lt. Ray Enners Award as the outstanding Division I player. He is Johns Hopkins University's all-time point leader. In 1978, he was selected the only single team captain in Johns Hopkins history.

O'Neill played for the U.S. Team in the 1982 World Lacrosse Championships. He played for the Chesapeake Lacrosse Club for three years and the Brine lacrosse Club for four years. He was an assistant coach at the University of Delaware in 1979, the University of North Carolina in 1980 and Brown University from 1981-84.