 He was elevated to a Privy Chamberlain of His Holiness on November 19, 1919, and later named rector of the Regional Seminary of Romagna.On June 30, 1930, Mimmi was appointed Bishop of Crema by Pope Pius XI.He received his episcopal consecration on the following July 25 from Cardinal Giovanni Nasalli Rocca di Corneliano, with Bishops Ettore Lodi and Giovanni Franzini serving as co-consecrators.