Guenther was the eldest son of Henry XXXI, Count of Schwarzburg-Blankenburg (1473–1526) and his first wife Magdalena of Hohnstein (1480–1504).

He introduced Protestantism in his country and fought on the Protestant side against the emperor in the Schmalkaldic War.

Günther benefitted considerably from the political downfall of the Ernestine branch of the House of Wettin.

To demonstrate his accumulated wealth and power, he largely demolished the existing castle in Sondershausen in 1533 and built a new Renaissance château on the site.

On 29 November 1528, Günther XL married Elisabeth (d. 14 May 1572), the daughter of Count Philip of Isenburg-Büdingen-Ronneburg.