| 20 April 1934 | Erected | Diocese of La Plata (Azul, Cachari, Chillar, Generat Belgrano, Las Flores, Pila, Ayacucho, Tandil, Rauch, Juárez, Tapalqné, General Alvear, Roque Pérez, Saladillo, XXV de Mayo, De la Riestra, Ernestina, Bolivar, Laprida, Olavarría, Hinojo, Colonias San Miguel, and General ..)
| Diocese of Azul (erected)
| | 11 February 1957 | Territory Lost | Diocese of Azul (Veinte y Cinco de Mayo)
Diocese of Mercedes (Nueve de Julio, Bragado, General Viamonte, Carlos Tejedor,
Pehuajó, Carlos Pellegrini, Rivadavia, General Villegas, General Pinto,
Lincoln, Carlos Casares, and Trenque-Lauquen)
| Diocese of Nueve de Julio (erected)
|