Date | Change |
| 1860.02.26 | Apostolic Prefecture of Zanguebar was established (from Diocese of Saint-Denis-de-La Réunion) |
| 1880.09.27 | Apostolic Vicariate of Tanganyika was established (from Apostolic Vicariate of Central Africa) |
| 1883.11.23 | Apostolic Prefecture of Zanguebar was promoted as Apostolic Vicariate of Zanguebar |
| 1887.01.11 | Apostolic Vicariate of Unianyembé was established (from Apostolic Vicariate of Tanganyika) |
| 1887.11.16 | Apostolic Vicariate of Zanguebar was renamed as Apostolic Vicariate of Northern Zanguebar (lost territory to establish Apostolic Prefecture of Southern Zanguebar) |
| 1887.11.16 | Apostolic Prefecture of Southern Zanguebar was established (from Apostolic Vicariate of Zanguebar) |
| 1894.07.13 | Apostolic Vicariate of Southern Victoria-Nyanza was established (from Apostolic Vicariate of Victoria-Nyanza) |
| 1902.09.15 | Apostolic Prefecture of Southern Zanguebar was promoted as Apostolic Vicariate of Southern Zanguebar |
| 1906.05.11 | Apostolic Vicariate of Central Zanguebar was established (from Apostolic Vicariate of Northern Zanguebar) |
| 1906.08.10 | Apostolic Vicariate of Southern Zanguebar was renamed as Apostolic Vicariate of Dar-es-Salaam |
| 1906.12.21 | Apostolic Vicariate of Central Zanguebar was renamed as Apostolic Vicariate of Bagamoyo |
| 1906.12.21 | Apostolic Vicariate of Northern Zanguebar was renamed as Apostolic Vicariate of Zanzibar |
| 1910.09.13 | Apostolic Vicariate of Kilima-Njaro was established (from Apostolic Vicariate of Bagamoyo) |
| 1913.11.12 | Apostolic Prefecture of Lindi was established (from Apostolic Vicariate of Dar-es-Salaam) |
| 1915 | Apostolic Vicariate of Southern Victoria-Nyanza was renamed as Apostolic Vicariate of Victoria-Nyanza |
| 1922.03.03 | Apostolic Prefecture of Iringa was established (from Apostolic Vicariate of Dar-es-Salaam) |
| 1925.05.31 | Apostolic Vicariate of Unianyembé was renamed as Apostolic Vicariate of Tabora |
| 1927.12.15 | Apostolic Prefecture of Lindi was promoted as Territorial Abbacy of Lindi |
| 1929.04.08 | Apostolic Vicariate of Bubuka was established (from Apostolic Vicariate of Northern Victoria-Nyanza and Apostolic Vicariate of Tabora) |
| 1929.04.10 | Apostolic Vicariate of Victoria-Nyanza was renamed as Apostolic Vicariate of Mwanza |
| 1931.12.22 | Territorial Abbacy of Lindi was suppressed (to establish Territorial Abbacy of Peramiho and Territorial Abbacy of Ndanda) |
| 1931.12.22 | Territorial Abbacy of Ndanda was established (from the suppressed Territorial Abbacy of Lindi) |
| 1931.12.22 | Territorial Abbacy of Peramiho was established (from the suppressed Territorial Abbacy of Lindi) |
| 1932.07.18 | Mission “sui iuris” of Tukuyu was established (from Apostolic Vicariate of Tanganyika) |
| 1935.01.28 | Apostolic Prefecture of Dodoma was established (from Apostolic Prefecture of Iringa, Apostolic Vicariate of Bagamoyo and Apostolic Vicariate of Kilima-Njaro) |
| 1938.03.29 | Mission “sui iuris” of Tukuyu was promoted as Apostolic Prefecture of Tukuyu |
| 1943.04.14 | Apostolic Prefecture of Mbulu was established (from Apostolic Prefecture of Dodoma and Apostolic Vicariate of Kilima-Njaro) |
| 1946.04.11 | Apostolic Vicariate of Musoma-Maswa was established (from Apostolic Vicariate of Mwanza) |
| 1946.05.10 | Apostolic Vicariate of Tanganyika was renamed as Apostolic Vicariate of Karema (lost territory to establish Apostolic Vicariate of Kigoma) |
| 1946.05.10 | Apostolic Vicariate of Kigoma was established (from Apostolic Vicariate of Tanganyika) |
| 1948.01.08 | Apostolic Prefecture of Iringa was promoted as Apostolic Vicariate of Iringa |
| 1949.07.14 | Apostolic Prefecture of Tukuyu was promoted as Apostolic Vicariate of Mbeya |
| 1950.04.18 | Apostolic Prefecture of Tanga was established (from Apostolic Vicariate of Kilima-Njaro) |
| 1950.06.24 | Apostolic Vicariate of Maswa was established (from Apostolic Vicariate of Musoma-Maswa) |
| 1950.06.24 | Apostolic Vicariate of Musoma-Maswa was demoted as Apostolic Prefecture of Musoma (lost territory to establish Apostolic Vicariate of Maswa) |
| 1951 | Apostolic Vicariate of Bubuka was promoted as Diocese of Bukoba |
| 1951.05.10 | Apostolic Prefecture of Dodoma was promoted as Apostolic Vicariate of Dodoma |
| 1951.12.13 | Apostolic Vicariate of Lower Kagera was established (from Apostolic Vicariate of Bubuka) |
| 1952.01.10 | Apostolic Prefecture of Mbulu was promoted as Apostolic Vicariate of Mbulu |
| 1953.03.25 | Apostolic Vicariate of Dar-es-Salaam was promoted as Metropolitan Archdiocese of Dar-es-Salaam |
| 1953.03.25 | Apostolic Vicariate of Dodoma was promoted as Diocese of Dodoma |
| 1953.03.25 | Apostolic Vicariate of Iringa was promoted as Diocese of Iringa |
| 1953.03.25 | Apostolic Vicariate of Karema was promoted as Diocese of Karema |
| 1953.03.25 | Apostolic Vicariate of Kigoma was promoted as Diocese of Kigoma |
| 1953.03.25 | Apostolic Vicariate of Maswa was promoted as Diocese of Maswa |
| 1953.03.25 | Apostolic Vicariate of Mbeya was promoted as Diocese of Mbeya |
| 1953.03.25 | Apostolic Vicariate of Mbulu was promoted as Diocese of Mbulu |
| 1953.03.25 | Apostolic Vicariate of Bagamoyo was promoted as Diocese of Morogoro |
| 1953.03.25 | Apostolic Vicariate of Kilima-Njaro was promoted as Diocese of Moshi |
| 1953.03.25 | Apostolic Vicariate of Mwanza was promoted as Diocese of Mwanza |
| 1953.03.25 | Apostolic Vicariate of Lower Kagera was promoted as Diocese of Rutabo |
| 1953.03.25 | Apostolic Vicariate of Tabora was promoted as Metropolitan Archdiocese of Tabora |
| 1953.03.25 | Apostolic Vicariate of Zanzibar was suppressed (to establish Metropolitan Archdiocese of Nairobi) |
| 1956.08.09 | Diocese of Maswa was renamed as Diocese of Shinyanga |
| 1957.07.05 | Apostolic Prefecture of Musoma was promoted as Diocese of Musoma |
| 1958.02.24 | Apostolic Prefecture of Tanga was promoted as Diocese of Tanga |
| 1960.06.21 | Diocese of Bukoba was established (from the suppressed Diocese of Rutabo) |
| 1960.06.21 | Diocese of Bukoba was renamed as Diocese of Rulenge |
| 1960.06.21 | Diocese of Rutabo was suppressed (to establish Diocese of Bukoba) |
| 1963.03.01 | Diocese of Arusha was established (from Diocese of Moshi) |
| 1963.08.05 | Diocese of Nachingwea was established (from Territorial Abbacy of Ndanda) |
| 1963.12.10 | Apostolic Prefecture of Same was established (from Diocese of Moshi) |
| 1964.04.21 | Diocese of Mahenge was established (from Metropolitan Archdiocese of Dar-es-Salaam) |
| 1964.12.12 | Apostolic Administration of Zanzibar e Pemba was restored (from Metropolitan Archdiocese of Dar-es-Salaam and Diocese of Mombasa e Zanzibar) |
| 1968.02.16 | Diocese of Njombe was established (from Territorial Abbacy of Peramiho and Diocese of Iringa) |
| 1969.02.06 | Territorial Abbacy of Peramiho was promoted as Diocese of Songea |
| 1969.10.24 | Diocese of Karema was renamed as Diocese of Sumbawanga |
| 1972.03.25 | Diocese of Singida was established (from Metropolitan Archdiocese of Tabora, Diocese of Dodoma and Diocese of Mbeya) |
| 1972.12.18 | Territorial Abbacy of Ndanda was promoted as Diocese of Mtwara |
| 1977.02.03 | Apostolic Prefecture of Same was promoted as Diocese of Same |
| 1980.03.28 | Apostolic Administration of Zanzibar e Pemba was promoted as Diocese of Zanzibar |
| 1983.11.11 | Diocese of Kahama was established (from Metropolitan Archdiocese of Tabora) |
| 1984.11.08 | Diocese of Geita was established (from Diocese of Mwanza) |
| 1986.10.17 | Diocese of Lindi was restored (from the suppressed Diocese of Nachingwea) |
| 1986.10.17 | Diocese of Nachingwea was suppressed (to establish Diocese of Lindi and Diocese of Tunduru–Masasi) |
| 1986.10.17 | Diocese of Tunduru–Masasi was established (from the suppressed Diocese of Nachingwea) |
| 1986.12.22 | Diocese of Mbinga was established (from Diocese of Songea) |
| 1987.11.18 | Diocese of Mwanza was promoted as Metropolitan Archdiocese of Mwanza |
| 1987.11.18 | Diocese of Songea was promoted as Metropolitan Archdiocese of Songea |
| 1999.03.16 | Diocese of Arusha was promoted as Metropolitan Archdiocese of Arusha |
| 2000.10.23 | Diocese of Mpanda was established (from Diocese of Sumbawanga) |
| 2008.08.14 | Diocese of Kayanga was established (from Diocese of Rulenge) |
| 2008.08.14 | Diocese of Rulenge was renamed as Diocese of Rulenge–Ngara (lost territory to establish Diocese of Kayanga) |
| 2009.01 | Titular Episcopal See of Nachingwea was restored |
| 2009.01 | Titular Episcopal See of Rutabo was restored |
| 2010.11.27 | Diocese of Bunda was established (from Metropolitan Archdiocese of Mwanza and Diocese of Musoma) |
| 2011.03.12 | Diocese of Kondoa was established (from Diocese of Dodoma) |
| 2012.01.14 | Diocese of Ifakara was established (from Diocese of Mahenge) |
