The former Diocese of Hearst previously had 18 parishes and missions, with a Catholic population of approximately 20,045 which at the time was served by 21 diocesan priests, two permanent deacons and three religious Sisters. 

The former Diocese of Moosonee had 14 parishes and missions, with a Catholic population of approximately 3,830 and this was served by five priests who were members of institutes of consecrated life. 

The new Diocese of Hearst-Moosonee currently has 25 parishes, 13 missions and approximately 27,080 Catholics. The seat of the ecclesiastical district will be located in Hearst.