His father died in 1329, and he remained under guardianship until 1344, when he came of age and began to carry a seal as a participant in the governance of Mecklenburg.

On 8 July 1348, Holy Roman Emperor Charles IV raised John and his brother Albert II to the rank of Duke in Prague.

Upon the division of Mecklenburg on 25 November 1352, John was awarded the Lordships of Stargard, Sternbuerg and Ture.

He supported his nephew Albert III of Mecklenburg in his attempts to be recognized as King of Sweden.

John's third wife Agnes was the daughter of Ulrich II of Lindow-Ruppin and widow of Lord Nicholas IV of Werle.