Arrived in Naples when he was 12 years old, Santoro briefly enrolled at the Accademia, under the teaching of Domenico Morelli, but he abandoned it for his intolerance to discipline. He perfected his art through the numerous trips in Italy and abroad, with frequent stays in Venice, Verona, Chioggia. In 1874, at the age of 15, he debuted with three works at the Promotrice Napoletana. In the summer of the same year Santoro met Mariano Fortuny, who strongly influenced his art and was, also, the way to contact the International art market. Many of his Amalfi landscapes were bought by the Goupil Gallery in Paris and he also worked for Colnaghi, the art dealer in London.