Maurice's successor Augustus confirmed his tariff privilege on the salt trade in Frankenhausen.

After his father's death, John Günther I initially ruled Schwarzburg jointly with his three brothers.

He fought in the Netherlands alongside his eldest brother Günther XLI and distinguished himself during the conquest of Saint-Quentin in 1583.

After his brothers Günther XLI of Schwarzburg-Arnstadt and William I of Schwarzburg-Frankenhausen had died without male heirs, John Günther I inherited Schwarzburg-Arnstadt and his remaining brother Albert VII inherited Schwarzburg-Frankenhausen.

John Gunther married on 16 February 1566 with Anna (1539–1579), daughter of Anthony I, Count of Oldenburg.