In mid-1994, he joined Parma A.C. of Serie A, which he made his debut on 18 September 1994, in a 2–1 home win against Cagliari Calcio.
In August 2003, Castellini was re-signed by UEFA Cup competitor Parma for a reported 3-year contract.
The friendly match ended in 1–0 won and Castellini played as Fabio Cannavaro's substitute in the 55th minute.
With the effort of Francesco Antonioli and other members of the defensive line including Castellini, the Genoese team finished fifth and conceded the third fewest goals.
A surplus for young Sampdoria, Along with Francesco Antonioli, Castellini were signed by Serie A newcomer Bologna in June 2006.
Along with Antonioli, the duo released again after Bologna almost failed to avoid relegation back to Serie B. Castellini made his only senior international appearance for Italy under manager Giovanni Trapattoni, on 16 November 2003, in a 1–0 friendly home win over Romania.