After their father's death in 1581 the then major Maurice and his elder brothers Magnus II and Francis II jointly ruled as dukes in Saxe-Lauenburg.
In 1585 (or 1586) Maurice moved to Buxtehude, then a city in the Prince-Archbishopric of Bremen ruled by his brother Prince-Archbishop Henry of Saxe-Lauenburg, and resided in Buxtehude in the Abtshaus (Abbot's house) of the nunnery of (now a component of Buxtehude).