It should not be confused with the smaller Prince-Bishopric of Osnabrück–an ecclesiastical principality of the Holy Roman Empire until 1803–over which the bishop, as prince-bishop, exercised both temporal and spiritual authority.

The temporal possessions of the see, originally quite limited, grew in time, and its prince-bishops exercised an extensive civil jurisdiction within the territory covered by their rights of immunity.

While the prince-bishopric was ruled by a Protestant bishop, the Archbishop of Cologne would oversee the exercise of the Catholic religion in Osnabrück.

In the German Mediatisation of 1803, the bishopric was dissolved and given to the Hanover branch of Brunswick-Lüneburg; the see, the chapter, the convents and the Catholic charitable institutions were finally secularized.

Klemens von Gruben, titular Bishop of Paros, was made vicar Apostolic, and as such cared for the spiritual interests of the Catholic population.

Under Pope Leo XII the papal bull Impensa Romanorum Pontificum (26 March 1824) re-established the See of Osnabrück as an exempt see, i.e., immediately subject to Rome.

Pope Pius IX, with the consent of King George V of Hanover, appointed Paulus Melchers of Münster as bishop on 3 August 1857.