Pache was born in Verdun, but grew up in Paris, of Swiss parentage, the son of the concièrge of the hotel of Marshal de Castries.

He became tutor to the marshal's children, and subsequently first secretary at the ministry of marine, head of supplies (munitionnaire général des vivres), and comptroller of the king's household.

[1] He was employed successively at the ministries of the interior and of war, and was appointed on 20 September 1793 third deputy suppliant of Paris by the Luxembourg section.

[citation needed] He was supported, however, by Marat, and when he was superseded in the ministry of war by Beurnonville (4 February 1793) he was chosen mayor by the Parisians.

[1] Jean Nicolas Pache would be the first to submit a petition to the National Convention on 15 April 1793 for the totemic 22 Girondist leaders to be removed from office.