His musical education was supported by Count Ferdinand Otto von Traun, who allowed him to study at the Naples Conservatory, as a pupil of Leonardo Leo and Francesco Durante.
[1] In the middle of the 1740s, he made several European tours as a member of the ensemble of Phillip Nicolini, specialised in children mime (Teatro dell'Opera Pantomima dei Piccolo Hollandesi di Nicolini).
In 1762, Fiorillo was engaged by Frederick II, Landgrave of Hesse-Cassel at his court in Kassel.
His output include operas, intermezzos and stage music for Nicolini's ensemble.
His composing style is similar to Johann Adolph Hasse, with apparent melodic invention and with dramatic expression concentrated in the vocal parts.