In 1948, he made his debut at the Teatro alla Scala in Milan, as Nadir in Les pêcheurs de perles, later singing Ramiro in La cenerentola, which he also sang that same year at the Verona Arena.
The tenor sang regularly in Naples and Bologna, and made guest appearances at the New York City Opera in 1947: La traviata (with Enzo Mascherini as Giorgio), Rigoletto (opposite Giuseppe Valdengo and Virginia MacWatters), Madama Butterfly, La bohème, Il barbiere di Siviglia (conducted by Julius Rudel) and Don Giovanni (in Theodore Komisarjevsky's production).
In 1964 Infantino reprised his role of Edgardo at the Bombay Opera in India, with soprano Celia Baptista as his Lucia.
He was also active throughout his career singing on Italian Radio (RAI), where he gave his last performance in 1973, in Mannino's Il diavolo in giardino.
A stylish lyric tenor with an attractive voice, Infantino can be heard in complete recordings of La traviata (EMI, 1946) and Il barbiere di Siviglia (Cetra, 1950, opposite Giuseppe Taddei and Giulietta Simionato).