Together first with his brother and then with his nephews, Nicholas was the co-ruling Count of Holstein-Rendsburg from 1340 until his death.

He was thus a leading member of the House of Schauenburg and an influential figure in the area north of the Elbe.

He was the second son of Count Gerhard III of Holstein-Rendsburg and his wife, Sophia of Werle.

[1] In 1354, he married Elisabeth, the daughter of Duke William II of Brunswick and Lüneburg, Prince of Lunenburg.

His nephew Gerhard VI acted as guardian for his underage daughter Elisabeth.