His mother, Countess Sophie Charlotte of Leiningen-Westerburg, was heavily influenced by Pietism and raised her son in this spirit.

Henry Ernest studied at the universities in Halle and Göttingen and, already in 1739, he received a prebend at the cathedral chapter at Halberstadt; this appointment was confirmed by King Frederick II of Prussia.

His father involved him in the ruling of the county from a young age and after 1742 he consistently attended meetings of the Chamber of Wernigerode.

After his father's death on 25 October 1771, the 55-year-old Henry Ernest took up the government in the county of Wernigerode, where he promoted the most pietistic form of religious life.

Henry Ernest was married on 11 December 1738 in Sorau to Marie Elizabeth, daughter of Count Erdmann II of Promnitz.