Born in Subbiano, Italy, Antonelli joined the Order of Friars Minor in Florence in 1909, becoming a Professed Member of the Order of Friars Minor in April 1914.

Antonelli was a faculty member of the Pontifical Antonianum Athenaeum, Rome, from 1928 to 1965, was Rector Magnifico from 1937 to 1943, and 1953 to 1959.

[2] On 19 February 1966 he was appointed Titular Archbishop of Idicra and was consecrated on 9 March 1966.

On 7 May 1969 Antonelli was appointed secretary of the Congregation for the Causes of Saints, and on 5 March 1973 he was elevated to Cardinal-Deacon of San Sebastiano al Palatino, on the same day resigning as secretary of the Congregation for the Causes of Saints.

He was appointed Cardinal-Priest of San Sebastiano al Palatino on 2 February 1983.