He was previously an assistant coach for the Houston Rockets, Boston Celtics, Cleveland Cavaliers, Washington Wizards, Sacramento Kings and Atlanta Hawks, winning an NBA Finals championship with both the Celtics and Cavaliers.
Adelphi made two consecutive NCAA Division II Men's Basketball Championship appearances in 1998 and 1999.
In 2000, he took a job as an assistant coach at Lafayette College, where he helped guide the team to a Patriot League Title and an NCAA Tournament appearance.
In his first season with the Celtics, the team went on to win the NBA Championship, defeating the Los Angeles Lakers 4–2.
In 2016, Longabardi was hired by the Cleveland Cavaliers to be their defensive coordinator under head coach Tyronn Lue.