He did not come from a wealthy family, and was discouraged by his family from pursuing a musical career, but with the aid an aunt, he was eventually allowed to apply for admission to the San Pietro di Majella Conservatory in Naples. There he was befriended by Francesco Florimo, a librarian, archivist, and teacher who encouraged him and introduced him to the music of Bellini
, who became a lifelong inspiration. At first, he showed more promise as an instrumental composer than an operatic one, and some of his piano works were published by Ricordi while he was still a student. Upon graduating in 1889, he had modest successes with his first two operas, Gina and La Tilda, but achieved somewhat wider fame with L'arlesiana, premiered in 1897 (revised in 1898 and yet again in 1937.) However, not achieving the level of success he had hoped for, he had to be persuaded by his publisher, Sonzago, to continue writing rather than concentrating on music education. Upon graduating, he had taken a position as auxiliary professor of harmony and piano at the Conservatory.
In 1900, he began work on Adriana Lecouvreur, and it premiered in 1902, with the young Enrico Caruso
, who had also sung the tenor lead, Federico, in L'arlesiana. In 1904, Cilea was popular enough that the Theatre Sarah Bernhardt in Paris was able to mount a season consisting solely of his works.
In 1907, his opera Gloria had its premiere at La Scala, conducted by Toscanini
. It is far different from his previous operas, with a wide dramatic scope, extensive choral writing, and considerably more sophisticated orchestral writing. However, it was not as successful as he hoped, either at its premiere or in the revised version staged in 1932, and except for one tribute to Verdi
(Il canto della vita) and the above-mentioned revisions to his other works, Cilea essentially stopped composing, and instead returned his focus to music education, teaching at the Palermo and Naples conservatories, among others.