After the death of his father, he took up residence in Bützow and succeeded his cousin Duke Magnus III of Mecklenburg-Schwerin as Lutheran administrator of the Prince-Bishopric of Schwerin in 1550.

Ulrich participated in the exchange with Tycho Brahe and David Chytraeus in the scientific discourse of his time and corresponded with humanists like Heinrich Rantzau.

As Administrator of the Prince-Bishopric of Schwerin he was succeeded by his grandson the last Bishop of Schleswig, Prince Ulrich of Denmark (30 December 1578 – 27 March 1624 in Rühn), who married with Lady Catherine Hahn-Hinrichshagen.

He sent his ambassadors to his wife's family and allies, to discuss his right to Elizabeth's throne and that the Princes of Europe should supported him against Spanish claims, with military help if required.

Ulrich wrote to James on 20 August with a letter of cautious support, counselling that Elizabeth should name him her successor, and was lukewarm on a definite pledge of arms.