Raised to the rank of Privy Chamberlain of His Holiness on 18 May 1911, Massimi was made auditor (29 November 1915), pro-dean (19 February 1924), and dean (1 May 1926) of the Roman Rota.
Massimi was elevated to a prominent role as Privy Chamberlain of His Holiness in 1911. He subsequently assumed key positions, including auditor (29 November 1915), pro-dean (19 February 1924), and dean (1 May 1926) of the Roman Rota.