He played seven seasons for Pittsburgh, registering 133 saves, which ranks third in franchise history.
He split time between Oakland and the Chicago Cubs in 1977 before retiring.
A native of Seneca Falls, New York, Giusti played collegiately at Syracuse before being signed by Houston, then an expansion team known as the Colt .45s, as an amateur free agent.
He appeared in 22 games as a rookie in 1962, spent all of 1963 in the minors before returning to the majors for good after being called up during the 1964 season.
Giusti is survived by his wife, two daughters and four grandchildren.