Without achieving the notoriety of some of his more famous revolutionary colleagues, he held a number of key positions - President of the National Constituent Assembly (20 July - 1 August 1790), President of the National Convention (27 December 1792 – 10 January 1793, coinciding with the trial of Louis XVI, three-time member of the Committee of Public Safety (7 April 1793 – 12 June 1793; 31 July 1794 - 5 November 1794; 4 May 1795 – 2 August 1795), chairman of the Council of Five Hundred, member of the French Directory.

Eugene Marbeau describes Jean-Baptiste Treilhard as "a man honest and right, who is content to do his duty in the situation... but who does not seek... to dominate events".

Jean Baptiste was a student at the collège des doctrinaires (now the Hôtel de Ville) at Brive, where he received an education balancing the requirements of science and faith.

His most important early role was in the Comité ecclésiastique (Ecclesiastical Committee) where he took the lead in promoting the Civil Constitution of the Clergy, a major reorganization of the Roman Catholic Church (including the suppression of its monasteries and the nationalization of its property).

In 1795, he arranged the exchange of the daughter of Louis XVI, Marie Thérèse of France, future Duchess of Angoulême, who was a prisoner of the Republic since autumn 1792, for the commissioners to armies betrayed by the general Dumoriez and turned over to the Austrians in spring 1793.

Treilhard became one of five Directors, the chief executive body of France, 15 May 1798 (26 Floréal year VI)[1] in replacement of François de Neufchâteau.

Under the Directory, he entered the Council of Five Hundred, of which he was president during the month of Nivôse, Year IV,[1] and was a member of the Court of Cassation, as well plenipotentiary at the Second Congress of Rastatt (December 1797).