He began his education in mathematics in order to train for the Engineer Corps, but his interest lay in architecture, which he studied enthusiastically.

When the Royal Danish Academy of Art (Det Kongelige Danske Kunstakademi) opened in 1754 at Charlottenborg Palace he was able to study under French architect Nicolas-Henri Jardin.

In 1756 his design for a city gate won the Academy’s large gold medallion, giving him the distinction of being the first Danish architect to win the coveted award.

That same year he was invited to join the Academy, and received the assignment to design "Et kongeligt Palais, liggende paa en smuk Plads" ("A royal palace located on a beautiful plaza").

Between 1766-1769 he built the memorial chapel for former Lord High Steward Count Adam Gottlob Moltke at Karise Church in Faxe, which had been begun by his former teacher and now fellow Professor at the Academy architect Nicolas-Henri Jardin.

The neoclassical wood pulpit is painted to look like golden marble, and features a frieze attributed to Johannes Wiedewelt and Peder Als.

In 1774-1779 he designed and started building the austere memorial chapels for Christian VI and Frederik V at Roskilde Cathedral.

[7] In May 1770 Harsdorff married the widow Elisabeth (Elsebeth) Margrethe Braun, daughter of Building Master to the royal court Jacob Fortling.

The couple had three children of whom two daughters survived In May 1799 he became sick at his country home Rosenlund on Gammel Kongevej, Frederiksberg, and he died there on 24 May 1799.