In 1979, Lancellotti was named the Eastern League most valuable player after lead the league with 41 home runs and 107 runs batted in while playing for the Buffalo Bisons, the Double-A affiliate of the Pittsburgh Pirates. He made his Major League debut with the San Diego Padres in , appearing in just 17 games. His career-highlight came in , when he led all professional baseball with 131 RBI and hit 29 home runs while playing for Triple-A Las Vegas, a San Diego affiliate.
In , Lancellotti led the Pacific Coast League with 31 home runs while playing for Phoenix, at the time the Giants' Triple-A affiliate. At 30, he was promoted to the big club and hit .222 with two home runs and six RBI in 18 at-bats. In and he played in Japan, hitting 58 home runs in 190 games for Hiroshima, including a league-leading 39 homers in 1987. Two years later he played in the now defunct Senior Professional Baseball Association.
Lancellotti did not win another chance in the Majors until August 1990, when he played four games for the Boston Red Sox and went 0-for-8. Before the promotion he had 10 home runs for Triple-A Pawtucket. He returned just in time to finished the month with 11 home runs to win the International League title with 21. Lancellotti was named the best player in the Red Sox farm system by the Boston Sportswriters Association. At the same time, Boston released him. In , he played for the Parma Angels of Italy, being named the Best Hitter during the European Cup held in Holland. He hung up his spikes after the season and settled in Buffalo, New York, where he established a baseball school in 1993. He still owns and operates this school to the day.
In a three-season Major League career, Lancellotti was a .169 hitter with two home runs and 11 RBI in 36 games. He belted 276 home runs in his distinguished minor league career, setting a mark that still stands to this day.
Lancellotti gained induction into the Buffalo Baseball Hall of Fame in August 1995.