He received a diploma in violin and viola from the Luigi Cherubini Conservatory in Florence, and also studied composition there with Luigi Dallapiccola. He also studied at the Accademia Musicale Chigiana in Siena and at the Universität Mozarteum Salzburg. Subsequently he studied conducting with Igor Markevitch, Rafael Kubelík, and Leonard Bernstein. With Bernstein he studied at the Berkshire Music Center at Tanglewood. On 10 August 1951 he conducted a performance of Maurice Ravel's Ma mère l'oye ("Mother Goose") at Tanglewood's main shed.
In 1954-1956 he was conductor of the Tri-City Symphony Orchestra (now the Quad City Symphony Orchestra) in Davenport, Iowa. He was the conductor of the Oakland Symphony Orchestra 1955-1959 and the Oregon Symphony (then the Portland Symphony Orchestra) 1959-1961. He declined to conduct the next season with Portland due to having so many engagements elsewhere.
In 1960, he made his debut at La Scala, Milan with George Frideric Handel’s opera Serse in the original version. In 1961, he became guest conductor at La Scala. He became the permanent conductor of the RAI Orchestra in Turin (Orchestra di Torino della Radiotelevisione Italiana RAI) in 1967.
Piero Bellugi taught master classes at several institutions including the Accademia Musicale Chigiana in Siena, the University of California, Berkeley, and the New England Conservatory of Music in Boston. From 1996 he gave classes at the Luigi Cherubini Conservatory in Florence. David Spiro, Chiara Benati and Filippo Faes were among his students of conducting. He guest conducted for numerous orchestras and opera companies including the Aix-en-Provence Festival, Festival Canada in Ottawa, Rome Opera, Paris Opera, Santa Cecilia Orchestra, Lyric Opera of Chicago, and the San Francisco Opera. He was also a permanent conductor of the Italian Youth Orchestra (Orchestra Giovanile Italiana) and the Toscanini Orchestra of Parma.
Piero Bellugi conducted the premiere of Darius Milhaud's Symphony No. 10 (in 1961) and Goffredo Petrassi's Settimo Concerto (in 1965). According to the conductor's web site  Piero Bellugi's repertory spanned "from the music of Monteverdi, to that of avant-garde composers, and has presented many world premiéres (Berio, Bussotti, Milhaud, Messiaen, Nono, Penderecki etc.)”.
His son David Bellugi is a recorder virtuoso.
- “Conductor Piero Bellugi Named Artistic Director at Palermo's Opera House”, Andante. January 9, 2004.
- International Who’s Who in Classical Music (2004). New York: Europa.
- "Music World" New York Times, July 15, 1962, page 71.
- "Tanglewood on Parade with Eleanor Roosevelt" New York Times, August 19, 1951, page 17.