Achille Locatelli studied at the Seminary of Monza and at the Pontifical Roman Seminary trays Catholic theology and philosophy and received on 23 December 1879 in Milan, the sacrament of Holy Orders. He then continued his studies at the Pontifical Ecclesiastical Academy. 1886 staff of the Apostolic Nunciature in the Kingdom of Bavaria. Further stations of his diplomatic career until 1899 were Belgium, France and Austria. From 1899 to 1904 he worked in the department for special ecclesiastical affairs of the Vatican Secretariat of State. In 1905, he worked briefly at the Apostolic Nunciature of the Netherlands and traveled as a Papal envoy to the wedding celebrations of the Spanish King Alfonso XIII ..
1906 appointed him Titular Archbishop Pius X of Thessalonica and Apostolic Internuncio in Argentina, Paraguay and Uruguay. The bishop ordained by Cardinal Achille Locatelli Rafael Merry del Val y Zulueta. 1918 Pope Benedict XV appointed him. Apostolic Nuncio to Portugal. Pope Pius XI. took him in 1922 as a cardinal priest with the titular church of San Bernardo alle Terme in the College of Cardinals to. Achille Locatelli died on April 5, 1935 in Rome and was buried in Seregno.