After studying at Leipzig and Göttingen he entered the Hanoverian civil service in 1770 as councillor of the board of domains ("Kammerrat"); but, finding his advancement slow, he set out — on the advice of King George III of the United Kingdom — on a series of travels, spending some time at Wetzlar, Regensburg (where he studied the mechanism of the Imperial government), Vienna and Berlin. He also visited France, the Dutch Republic and Great Britain, where he was received kindly by the King. On his return, he married, at his father's suggestion, the Countess Christiane von Reventlow (1759–1793) in 1774. They had a son, Christian Heinrich August Graf von Hardenberg-Reventlow (1775–1841), and a daughter, Lucie von Hardenberg-Reventlow (1776-1854).