| Date | Country | Change |
| 1912 | Metropolitan Archdiocese of Calcutta lost territory to Apostolic Vicariate of Tibet 西藏 | |
| 1912 | Diocese of Cajamarca exchanged territory with Diocese of Trujillo | |
| 1912 | Diocese of Trujillo exchanged territory with Diocese of Cajamarca | |
| 1912.03.08 | Diocese of Kearney was established (from Diocese of Omaha and became suffragan of Dubuque) | |
| 1912.03.23 | Apostolic Vicariate of Brownsville was suppressed (to establish Diocese of Corpus Christi) | |
| 1912.03.23 | Diocese of Corpus Christi was established (from the suppressed Apostolic Vicariate of Brownsville and became suffragan of New Orleans) | |
| 1912.04.20 | Diocese of Tarbes was renamed as Diocese of Tarbes et Lourdes | |
| 1912.04.27 | Apostolic Vicariate of Coastal Chi-Li 直隸海濱 was established (from Apostolic Vicariate of Northern Chi-Li 直隸北境) | |
| 1912.06.01 | Apostolic Prefecture of South Solomons was promoted as Apostolic Vicariate of South Solomons | |
| 1912.06.08 | Diocese of Hajdúdorog (Hungarian Rite) was established (from Metropolitanate sui juris of Făgăraş şi Alba Iulia, Metropolitan Archdiocese of Esztergom, Diocese of Gherla, Armenopoli, Szamos-Ujvár, Diocese of Mukačeve, Diocese of Oradea Mare and Diocese of Prešov and became suffragan of Esztergom) | |
| 1912.06.15 | Apostolic Exarchate of Canada (Ukrainian Rite) was established | |
| 1912.06.20 | Mission sui juris of San Andrés y Providencia was established (from Metropolitan Archdiocese of Cartagena) | |
| 1912.08.13 | Apostolic Prefecture of Niigata 新潟 was established (from Metropolitan Archdiocese of Tokyo 東京, Diocese of Hakodate 函館 and Diocese of Osaka 大阪 and became suffragan of Tokyo 東京) | |
| 1912.10.04 | Apostolic Prefecture of Putumayo was established (from Apostolic Prefecture of San León del Amazonas) | |
| 1912.11.30 | Diocese of Calgary was established (from Diocese of Saint Albert and became suffragan of Edmonton) | |
| 1912.11.30 | Diocese of Saint Albert was promoted as Metropolitan Archdiocese of Edmonton (with suffragan see Calgary and lost territory to establish Diocese of Calgary) | |
| 1912.12.10 | Diocese of Camagüey was established (from Metropolitan Archdiocese of Santiago and became suffragan of Santiago) | |
| 1912.12.10 | Diocese of Matanzas was established (from Diocese of La Habana and became suffragan of Santiago) | |
| 1912.12.12 | Apostolic Vicariate of Kivu was established (from Apostolic Vicariate of Southern Victoria-Nyanza and Apostolic Vicariate of Unianyembé) |
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