Date | Country | Change |
| 1977 |  India | Titular Episcopal See of Chayal (Syro-Malankara Rite) was established |
| 1977.01.01 |  Italy | Metropolitan Archdiocese of Genova lost territory to Diocese of Livorno |
| 1977.01.01 |  USA | Abbacy nullius of Belmont–Mary Help of Christians was suppressed (to Diocese of Charlotte) |
| 1977.01.21 |  Congo-Kinshasa | Metropolitan Archdiocese of Lubumbashi lost territory to Diocese of Kilwa |
| 1977.02.03 |  Angola | Diocese of Nova Lisboa was promoted as Metropolitan Archdiocese of Huambo (with suffragan sees Benguela, Luso and Silva Porto) |
| 1977.02.03 | Angola | Diocese of Sá da Bandeira was promoted as Metropolitan Archdiocese of Lubango (with suffragan sees Pereira de Eça and Serpa Pinto) |
| 1977.02.03 | Angola | Diocese of Ngunza was renamed as Diocese of Novo Redondo |
| 1977.02.03 | India | Diocese of Khandwa was established (from Diocese of Indore and became suffragan of Bhopal) |
| 1977.02.03 |  Tanzania | Apostolic Prefecture of Same was promoted as Diocese of Same (became suffragan of Dar-es-Salaam) |
| 1977.02.22 | Italy | Diocese of Rimini exchanged territory with Diocese of Montefeltro |
| 1977.02.22 | Italy,  San Marino | Diocese of Montefeltro was renamed as Diocese of San Marino–Montefeltro (lost territory to Diocese of Sarsina, exchanged territory with Diocese of Rimini and became suffragan of Ravenna) |
| 1977.02.26 | India | Apostolic Exarchate of Bijnor (Syro-Malabar Rite) was promoted as Diocese of Bijnor |
| 1977.02.26 | India | Apostolic Exarchate of Chanda (Syro-Malabar Rite) was promoted as Diocese of Chanda (became suffragan of Nagpur) |
| 1977.02.26 | India | Apostolic Exarchate of Jagdalpur (Syro-Malabar Rite) was promoted as Diocese of Jagdalpur (became suffragan of Bhopal) |
| 1977.02.26 | India | Diocese of Kanjirapally (Syro-Malabar Rite) was established (from Metropolitan Archdiocese of Changanacherry and became suffragan of Changanacherry) |
| 1977.02.26 | India | Diocese of Rajkot (Syro-Malabar Rite) was established (from Diocese of Ahmedabad and became suffragan of Bombay) |
| 1977.02.26 | India | Apostolic Exarchate of Sagar (Syro-Malabar Rite) was promoted as Diocese of Sagar |
| 1977.02.26 | India | Apostolic Exarchate of Satna (Syro-Malabar Rite) was promoted as Diocese of Satna |
| 1977.02.26 | India | Apostolic Exarchate of Ujjain (Syro-Malabar Rite) was promoted as Diocese of Ujjain |
| 1977.03.01 | USA | Diocese of Biloxi was established (from the suppressed Diocese of Natchez–Jackson and became suffragan of New Orleans) |
| 1977.03.01 | USA | Diocese of Jackson was established (from the suppressed Diocese of Natchez–Jackson and became suffragan of New Orleans) |
| 1977.03.01 | USA | Diocese of Natchez–Jackson was suppressed (to establish Diocese of Biloxi and Diocese of Jackson) |
| 1977.03.02 | USA | Diocese of Houma–Thibodaux was established (from Metropolitan Archdiocese of New Orleans and became suffragan of New Orleans) |
| 1977.03.05 | Congo-Kinshasa | Diocese of Sakania was renamed as Diocese of Sakania–Kipushi |
| 1977.03.11 | USA | Metropolitanate sui juris of Munhall (Ruthenian Rite) was renamed as Metropolitanate sui juris of Pittsburgh |
| 1977.03.12 | India | Diocese of Guntur lost territory to Diocese of Nellore |
| 1977.03.21 |  Guinea-Bissau | Apostolic Prefecture of Guinea-Bissau was promoted as Diocese of Bissau (without ecclesiastical province) |
| 1977.03.21 | Italy | Provostry nullius of Atina was suppressed (to Territorial Abbacy of Montecassino) |
| 1977.03.21 | Italy | Territorial Abbacy of Montecassino lost territory to Metropolitan Archdiocese of Chieti, Diocese of Aquino, Diocese of Isernia, Diocese of Penne e Pescara, Diocese of Sessa Aurunca, Diocese of Sulmona, Diocese of Teano, Diocese of Trivento, Diocese of Valva and Diocese of Venafro |
| 1977.03.21 |  South Korea | Apostolic Prefecture of Cheju 제주 was promoted as Diocese of Cheju 제주 |
| 1977.04.02 |  Philippines | Diocese of Boac was established (from Diocese of Lucena and became suffragan of Lipa) |
| 1977.04.13 |  Mexico | Territorial Prelature of Nuevo Casas Grandes was established (from Diocese of Ciudad Juárez and became suffragan of Chihuahua) |
| 1977.04.20 |  U.S. Virgin Islands | Territorial Prelature of Virgin Islands was promoted as Diocese of Saint Thomas |
| 1977.04.26 |  Colombia | Diocese of Chiquinquirá was established (from Metropolitan Archdiocese of Tunja and became suffragan of Tunja) |
| 1977.04.26 | Colombia | Diocese of Garagoa was established (from Metropolitan Archdiocese of Tunja and became suffragan of Tunja) |
| 1977.05.30 |  Ghana | Diocese of Navrongo was renamed as Diocese of Navrongo–Bolgatanga (became suffragan of Tamale) |
| 1977.05.30 | Ghana | Diocese of Tamale was promoted as Metropolitan Archdiocese of Tamale (with suffragan sees Navrongo–Bolgatanga and Wa) |
| 1977.05.30 | India | Diocese of Baruipur was established (from Metropolitan Archdiocese of Calcutta and became suffragan of Calcutta) |
| 1977.06.27 | USA | Diocese of Saint Maron of Detroit (Maronite Rite) was renamed as Diocese of Saint Maron of Brooklyn |
| 1977.08.04 | Congo-Kinshasa | Diocese of Kilwa was renamed as Diocese of Kilwa–Kasenga |
| 1977.08.04 |  Lebanon | Diocese of Baalbek (Maronite Rite) was renamed as Diocese of Baalbek e Zahlé |
| 1977.08.04 | Lebanon | Diocese of Jounieh (Maronite Rite) was established |
| 1977.08.04 |  Syria | Titular Archiepiscopal See of Laodicea in Syria (Maronite Rite) was suppressed (to Diocese of Latakia) |
| 1977.08.04 | Syria | Apostolic Administration of Latakia (Maronite Rite) was promoted as Diocese of Latakia (gained territory from the suppressed Titular Archiepiscopal See of Laodicea in Syria and without ecclesiastical province) |
| 1977.08.26 |  Brazil | Diocese of Coroatá was established (from Metropolitan Archdiocese of São Luís do Maranhão and became suffragan of São Luís do Maranhão) |
| 1977.09.01 |  Pakistan | Diocese of Lyallpur was renamed as Diocese of Faisalabad |
| 1977.10.17 |  Croatia | Diocese of Poreč i Pula exchanged territory with Diocese of Koper |
| 1977.10.17 | Croatia | Metropolitan Archdiocese of Rijeka–Senj lost territory to Diocese of Koper |
| 1977.10.17 | Italy | Metropolitan Archdiocese of Gorizia e Gradisca lost territory to Diocese of Koper |
| 1977.10.17 | Italy | Diocese of Trieste was renamed as Diocese of Trieste (lost territory to Diocese of Poreč i Pula and exchanged territory with Diocese of Koper) |
| 1977.10.17 | Italy | Diocese of Trivento lost territory to Diocese of Sulmona |
| 1977.10.17 |  Slovenia | Diocese of Koper exchanged territory with Diocese of Poreč i Pula and Diocese of Trieste |
| 1977.10.28 | Italy | Diocese of Città della Pieve lost territory to Diocese of Sovana–Pitigliano |
| 1977.10.28 | Italy | Diocese of Montalcino lost territory to Diocese of Pienza |
| 1977.10.28 | Italy | Diocese of Pienza lost territory to Territorial Abbacy of Monte Oliveto Maggiore |
| 1977.10.28 | Italy | Metropolitan Archdiocese of Siena lost territory to Diocese of Montalcino |
| 1977.11.03 |  Portugal | Diocese of Viana do Castelo was established (from Metropolitan Archdiocese of Braga and became suffragan of Braga) |
| 1977.11.10 | India | Diocese of Ambikapur was established (from Diocese of Raigarh–Ambikapur and became suffragan of Bhopal) |
| 1977.11.10 | India | Diocese of Raigarh–Ambikapur was renamed as Diocese of Raigarh (lost territory to establish Diocese of Ambikapur) |
| 1977.11.10 |  Lesotho | Diocese of Mohale’s Hoek was established (from Metropolitan Archdiocese of Maseru and became suffragan of Maseru) |
| 1977.11.10 |  Nigeria | Diocese of Awka was established (from Metropolitan Archdiocese of Onitsha and became suffragan of Onitsha) |
| 1977.11.15 | Italy | Diocese of Ariano exchanged territory with Diocese of Bovino |
| 1977.11.15 | Italy | Diocese of Bovino exchanged territory with Diocese of Ariano |
| 1977.11.28 | Italy | Diocese of Acerenza was promoted as Archdiocese of Acerenza |
| 1977.12.03 |  Congo-Brazzaville | Diocese of Fort-Rousset was renamed as Diocese of Owando |
| 1977.12.03 | Italy | Diocese of Matera was promoted as Archdiocese of Matera (lost territory to Diocese of Castellaneta) |
| 1977.12.08 | Brazil | Diocese of Oeiras was renamed as Diocese of Oeiras–Floriano |
| 1977.12.17 | India | Diocese of Aurangabad was established (from Metropolitan Archdiocese of Hyderabad and Diocese of Amravati and became suffragan of Nagpur) |
| 1977.12.17 | Nigeria | Apostolic Prefecture of Idah was promoted as Diocese of Idah (became suffragan of Kaduna) |
| 1977.12.30 |  Ethiopia | Apostolic Prefecture of Hosanna was suppressed (to establish Apostolic Prefecture of Soddo–Hosanna) |
| 1977.12.30 | Ethiopia | Apostolic Prefecture of Soddo–Hosanna was established (from the suppressed Apostolic Prefecture of Hosanna) |
| 1977.12.30 |  Hungary | Diocese of Győr lost territory to Metropolitan Archdiocese of Trnava |
| 1977.12.30 | Hungary | Territorial Abbacy of Pannonhalma lost territory to Metropolitan Archdiocese of Trnava |
| 1977.12.30 |  Slovakia | Apostolic Administration of Trnava was promoted as Metropolitan Archdiocese of Trnava (with suffragan sees Banská Bystrica, Košice, Nitra, Rožňava and Spiš and gained territory from Diocese of Győr and Territorial Abbacy of Pannonhalma) |
