[3][4] As a junior player, she won 1996 French Open in doubles, while her best professional results include singles quarterfinals at the Internazionali Femminili di Palermo in 1999 and Tier I Italian Open in 2000, and three WTA Tour doubles titles.

She was a member of Italy Fed Cup team from 2000 to 2001, and won three doubles titles at WTA tournaments.

Casoni defeated players such as Dominique Monami, Katarina Srebotnik, Mariya Koryttseva, Francesca Schiavone, Émilie Loit and Nuria Llagostera Vives.

She also won four singles and 27 doubles titles on the ITF Women's Circuit.

Casoni retired from tennis in 2006, after struggling with a knee injury.