 | 1916 | 1917 | 1918 |  |
Date | Country | Change |
| 1917 |  Australia | Diocese of Goulburn lost territory to Metropolitan Archdiocese of Sydney |
| 1917 |  Russia | Apostolic Exarchate of Russia (Russian Rite) was established (from Metropolitan Archdiocese of Mohilev) |
| 1917.02.05 |  Colombia | Diocese of Antioquía was renamed as Diocese of Antioquía–Jericó (gained territory from the suppressed Diocese of Jericó and lost territory to establish Diocese of Santa Rosa de Osos) |
| 1917.02.05 | Colombia | Apostolic Prefecture of Chocó lost territory to Diocese of Jericó |
| 1917.02.05 | Colombia | Diocese of Jericó was suppressed (gained territory from Apostolic Prefecture of Chocó and to Diocese of Antioquía–Jericó) |
| 1917.02.05 | Colombia | Diocese of Santa Rosa de Osos was established (from Metropolitan Archdiocese of Medellín and Diocese of Antioquía and became suffragan of Medellín) |
| 1917.02.15 |  USA | Apostolic Prefecture of Alaska was promoted as Apostolic Vicariate of Alaska |
| 1917.04.11 | USA | Diocese of Grand Island was established (from the suppressed Diocese of Kearney and became suffragan of Dubuque) |
| 1917.04.11 | USA | Diocese of Kearney was suppressed (to establish Diocese of Grand Island) |
| 1917.06.13 |  Congo-Kinshasa | Apostolic Prefecture of Kasaï Supérieur was promoted as Apostolic Vicariate of Kasaï Supérieur |
| 1917.06.13 |  South Sudan | Apostolic Prefecture of Bahr el-Ghazal was promoted as Apostolic Vicariate of Bahr el-Ghazal |
| 1917.06.28 |  Brazil | Diocese of Diamantina was promoted as Metropolitan Archdiocese of Diamantina (with suffragan sees Araçuaí and Montes Claros) |
| 1917.07.20 |  England | Diocese of Brentwood was established (from Metropolitan Archdiocese of Westminster and became suffragan of Westminster) |
| 1917.07.28 | Australia | Diocese of Bathurst lost territory to Diocese of Wilcannia–Forbes |
| 1917.07.28 | Australia | Diocese of Wagga Wagga was established (from Diocese of Goulburn and became suffragan of Sydney) |
| 1917.07.28 | Australia | Diocese of Wilcannia was renamed as Diocese of Wilcannia–Forbes (gained territory from Diocese of Bathurst) |
| 1917.08.25 | Brazil | Diocese of Alagôas was renamed as Diocese of Maceió |
| 1917.12.01 |  Bolivia | Apostolic Vicariate of El Beni was established (from Diocese of Santa Cruz de la Sierra) |
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