He played eight seasons (from 1972 to 1980) in the National Basketball Association (NBA) with the New York Knicks, Buffalo Braves, Milwaukee Bucks, and Utah Jazz.

[6][7] Gianelli was sent from the Braves to the Bucks for a first-round pick in the 1979 NBA draft (eventually dealt to the Detroit Pistons) and cash nine months later on September 2, 1977.

He was traded along with the eighth overall selection in the first round of the 1979 NBA draft (Calvin Natt) from the Bucks to the New Jersey Nets for Harvey Catchings on May 31, 1979.

[9][10] He never appeared in a game with the Nets, as he was dealt along with Bernard King and Jim Boylan to the Jazz for Rich Kelley and cash on October 2.

[11] He averaged 7.8 points and 5.9 rebounds per game in his NBA career, and won a league championship with New York in 1973.