His political career began when, after taking part in the insurrection of Aug. 10, 1792, he became secretary of the Paris Commune and was elected to the National Convention, in which he sided with the more radical Montagnards against the Girondins. He voted for the execution of Louis XVI during the trial of the King (December 1792–January 1793). Later, as a member of the Committee of General Security, he was sent to organize army recruiting in southwestern France and to put down the rebels in Bordeaux.

Recalled to Paris in March 1794, Tallien initially supported the Committee of Public Safety, but he opposed the committee after it ordered the arrest of a noblewoman known as Madame Cabarrus, whom the Committee accused of being his mistress. Denounced by Robespierre (Robespierre, Maximilien de) on June 12, 1794, Tallien conspired with Paul Barras, Joseph Fouché, and others to overthrow him, which they did on July 27 (9 Thermidor).

After Robespierre's fall, Tallien became a leader of the Thermidorian Reaction, taking part in the suppression of members of the Revolutionary tribunals, the Jacobins, and some of his former colleagues whom he accused of being royalist sympathizers. As a member of the reconstructed Committee of Public Safety, he secured the release of Madame Cabarrus and married her on Dec. 26, 1794.

Under the Directory (1795–99), Tallien became a member of the Council of Five Hundred, but he had little influence because he was held suspect by all parties. He retained his seat until 1798, when he went to Egypt with Napoleon Bonaparte. Upon his return to Paris (April 1801), he divorced his wife, who had already deserted him.

Tallien supported the First Restoration (1814) and then the Hundred Days of Napoleon. Under the Second Restoration (1815), however, he was denied a pension and spent the rest of his life in poverty.