Jean-Baptiste Berthier was born on 6 January 1721 in Tonnerre, France.

After attracting the attention of marchal de camp Charles Louis Auguste Fouquet, duc de Belle-Isle, he was deputed by him to supervise construction of several prominent Paris public buildings, notably those of the ministries of war, navy and foreign affairs in Versailles.

In 1758, he was made Director of Military Survey to King Louis XV, a position he retained with Louis XVI for whom he prepared the famous topographic maps of the Royal hunting grounds.

[1] He married his first wife, Marie Françoise L'Huillier de La Serre, in 1746.

The oldest of five children, Louis Alexandre Berthier (1753), would become Marshal of France, with the other three sons also serving in the French Army: Charles (1760) in North America, while César (1765) and Victor-Léopold (1770) became generals during the Napoleonic Wars.