He was born in Bagnolo di Santa Fiora, Province of Grosseto, Tuscany. For thirty-six years Fr. Amantini, a Passionist stationed at the church of the Holy Staircase, was the chief exorcist of Rome. He would often see 60 to 80 people a day. Padre Pio said of him: "Father Candido is a priest after God's heart."
Father Gabriele Amorth became his apprentice, in June of 1986, and then eventually took over his position. After a painful illness, he died in Rome on the Feast of Saint Candido, his patron saint.