Raimondi's voice is actually somewhat closer to a bass-baritone than a true bass, but this did not prevent him from successfully singing most of the great bass roles — King Philip in Don Carlo, Fiesco in Simon Boccanegra, Boris Godunov, and Silva in Ernani being his most celebrated — as well as the roles more associated with bass-baritones, such as Escamillo, Mozart's Figaro, Don Alfonso in Così fan tutte, and Don Giovanni, and even a concert version of Scarpia. He is also quite celebrated as a singing actor, and has occasionally directed operas.
His voice matured early into its adult timbre, and at the age of 15, he auditioned for Francesco Molinari-Pradelli, who encouraged him in hopes for an operatic career. He began vocal studies with Ettore Campogalliani, and was accepted at age 16 as a student in the Milan Conservatory, where he studied with Teresa Pediconi and Antonio Piervenanzi.
He won the Adriano Belli Singing Competition and made his opera debut at the Spoleto Sperimentale (a program for young singers) as Colline in La bohème in 1964. This was followed shortly the same year by his Rome Opera debut as Procida in Verdi's I Vespri Siciliani, where he had been understudying for Nicola Rossi-Lemeni. Mario Labroca, of the Teatro La Fenice, heard of that performance, invited him to audition for him, and afterwards offered him a five-year contract for lead roles at that theater. There he worked with Leone Magiera, who taught him interpretation and vocal coloring, and Piero Faggioni, who taught him how to coordinate vocal production and physical motion. At the time, Raimondi was painfully shy and almost immovably stiff on stage, and almost incapable of vocal inflection, but the combined work of Magiera and Faggioni helped him develop into a singing actor.
His La Scala debut was as Timur in Turandot in 1968, his Met debut as Silva in 1970, and his Covent Garden debut was as Fiesco in 1972. In 1975, he made his Paris Opera debut as Procida, and his Salzburg Festival debut in 1980 as the King in Aida. In 1986, he first directed a production of Don Giovanni, and decided to continue his career as a director as well.
He also made some notable opera films, including the celebrated Joseph Losey Don Giovanni (1978); Escamillo in Francesco Rosi's 1984 film of Carmen, opposite Julia Migenes-Johnson (as she was then known) and Plácido Domingo; and the television film Six arias in search of a singer.
While his Scarpia did attract some controversy, the recording (DG) does show his powers as a singing actor, aristocratic, sinuous, and brutal. On Erato, he recorded a recital disc with scenes from many of his best-known roles.