Ninchi was born in Pesaro, the son of the actor Annibale.

In his youth he was a basketball player, debuting on the national team at just 17 years old.

[1] In 1959 he graduated from the Silvio D'Amico National Academy of Dramatic Art and began working on stage.

[1][2] His films include works directed by Claude Chabrol, Giuliano Montaldo, Lina Wertmüller, Pupi Avati, Silvio Soldini.

[2] He was cousin of the actress Ave Ninchi.