He studied mathematics in his birth town, Camerino, under his father Girolamo, a well-known and expert surveyor. He left Camerino for Rome to continue his mathematical studies (and started his architectural studies) at the "Sapienza" and at the Accademia di San Luca, participating in the 1754 Concorso Clementino in "classe II di Architettura". He was instructed in architecture by Marquis Gerolamo Theodoli, designer of the teatro Argentina. In 1755 Antinori went to Lisbon where he worked as architect in the "Casa dos Bicos" attending the reconstruction works after the earthquake of 1755, He also worked to the plans of a new palazzo reale of Campolide for Joseph I, but a short time later was imprisoned either due to envious accusations by his rivals or due to a conspiracy in which he had got involved. With the help of the Portuguese woman Josefa Luisa Lopez de Cunha, he escaped and fled to Italy, where he married her.