Born in Barcelona, he made his debut at the Gran Teatre del Liceu in his native city in the 1964–65 season, as Escamillo in Carmen.
His first appearance at the Teatro alla Scala was in 1967, as Enrico in Lucia di Lammermoor, opposite Renata Scotto, subsequently appearing there in Il trovatore (1978), I due Foscari (1980), and Falstaff (as Ford, conducted by Lorin Maazel, and directed by Giorgio Strehler, 1981).
Sardinero also sang at London's Covent Garden (Marcello in La bohème, 1976) and was often heard in zarzuela.
In 1968, he appeared at the New York City Opera, in Il barbiere di Siviglia and Pagliacci.
In 1977, Sardinero sang at the Metropolitan Opera, as Marcello in La bohème.