 | 1887 | 1888 | 1889 |  |
Date | Country | Change |
| 1888.03.05 |  USA | Apostolic Vicariate of Idaho lost territory to Diocese of Helena |
| 1888.03.20 |  Japan | Apostolic Vicariate of Central Japan 日本中部 was established (from Apostolic Vicariate of Southern Japan 日本南緯) |
| 1888.05.01 |  Turkiye | Diocese of Amida (Syriac Rite) was suppressed (to Diocese of Mardin and Amida) |
| 1888.05.01 | Turkiye | Diocese of Mardin (Syriac Rite) was renamed as Diocese of Mardin and Amida (gained territory from the suppressed Diocese of Amida) |
| 1888.05.04 |  Ethiopia | Apostolic Vicariate of Galla lost territory to Apostolic Vicariate of Aden |
| 1888.05.04 |  United Arab Emirates,  Oman,  Yemen | Apostolic Prefecture of Aden was promoted as Apostolic Vicariate of Aden (gained territory from Apostolic Vicariate of Galla) |
| 1888.05.04 | USA | Diocese of Saint Paul was promoted as Metropolitan Archdiocese of Saint Paul (with suffragan see Dakota) |
| 1888.05.11 |  Congo-Kinshasa | Mission sui juris of Congo Belge was promoted as Apostolic Vicariate of Congo Belge |
| 1888.06.10 |  Belize | Apostolic Prefecture of British Honduras was established (from Apostolic Vicariate of Jamaica and without ecclesiastical province) |
| 1888.08.03 |  Australia | Diocese of Hobart was promoted as Metropolitan Archdiocese of Hobart |
| 1888.08.10 | Australia | Diocese of Victoria was renamed as Diocese of Victoria–Palmerston |
| 1888.08.19 |  Malaysia | Apostolic Vicariate of Western Siam was promoted as Diocese of Malacca (became suffragan of Pondicherry) |
| 1888.09.07 |  Switzerland | Apostolic Administration of Ticino was promoted as Diocese of Lugano (without ecclesiastical province) |
| 1888.10.01 |  China | Mission sui juris of I-li 伊犁 was restored (from Apostolic Vicariate of Gansu 甘肅) |
| 1888.12.25 |  Albania | Territorial Abbacy of Shën Llezhri i Oroshit was established (from Diocese of Lezhë) |
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