[2] At the age of 19 he made his operatic debut as Macduff in Verdi's Macbeth at the Astra Theatre in Gozo and went on to become a prize winner at the Belvedere Hans Gabor Competition the same year.

[3] On November 2, 2012, the University of Malta presented Calleja with a Doctor of Literature Honoris Causa in acknowledgment of his achievements as an internationally renowned tenor.

Through these grants, students have purchased new instruments, participated in competitions, masterclasses and training, attended auditions in the UK and other countries, made recordings, and furthered their studies.

[17] Calleja made a guest appearance on Renée Fleming's album By Request, singing the role of Alfredo in the act 1 closing scene of La traviata.

His recording of "La donna è mobile" from Verdi's Rigoletto was featured in the soundtrack for the 2007 film No Reservations, starring Catherine Zeta-Jones.

Calleja appears as tenor Enrico Caruso in James Gray's 2013 film The Immigrant, which also features Joaquin Phoenix and Marion Cotillard.