He was born at Tarbes in Gascony. The name of Barère de Vieuzac, by which he continued to call himself long after the renunciation of feudal rights on the famous 4 August, was assumed from a small fief belonging to his father, a lawyer at Vieuzac. He began to practise as an advocate at the parliament of Toulouse in 1770, and soon earned a reputation as an orator; while his brilliant and flowing style as a writer of essays led to his election as a member of the Academy of Floral Games of Toulouse in 1788.
At the age of thirty, he married. Four years later, in 1789, he was elected deputy by the estates of Bigorre to the French States-General, which met in May. He had made his first visit to Paris in the preceding year. He at first belonged to the constitutional party; but he was less known as a speaker in the Assembly than as a journalist. His paper, the Point du Jour, according to Aulard, owed its reputation not so much to its own qualities as to the fact that the painter David, in his famous picture of the Tennis Court Oath, showed Barère kneeling in the corner and writing a report of the proceedings for posterity.
The reports of the debates of the National Assembly in the Point du Jour, though not inaccurate, are as a matter of fact very incomplete and very dry. After the flight of the king to Varennes, Barère passed over to the republican party, though he continued to keep in touch with the duke of Orleans, to whose natural daughter, Pamela, he was tutor. Barère, however, appears to have been wholly free from any guiding principle; conscience he had none, and his conduct was regulated only by the determination to be on the side of the strongest. After the close of the National Assembly he was nominated one of the judges of the newly instituted court of cassation from October 1791 to September 1792.
In 1792 he was elected deputy to the National Convention for the department of the Hautes-Pyrénées. At first he voted with the Girondists, attacked Robespierre, "a pygmy who should not be set on a pedestal," and at the trial of the king voted with the Mountain for the king's death "without appeal and without delay." He closed his speech with a sentence which became memorable: "the tree of liberty could not grow were it not watered with the blood of kings." Appointed member of the Committee of Public Safety on April 7 1793, he busied himself with foreign affairs; then, joining the party of Robespierre, whose resentment he had averted by timely flatteries, he played an important part in the second Committee of Public Safety -- after 17 July, 1793 -- and voted for the death of the Girondists. He was thoroughly unscrupulous, stopping at nothing to maintain the supremacy of the Mountain, and rendered it great service by his rapid work, by the telling phases of his oratory, and by his clear expositions of the problems of the day.
On 9 Thermidor (July 27, 1794) Barère hesitated, then he drew up the report outlawing Robespierre. In spite of this, in Germinal of the year III (March 21 to April 4 1795), the Thermidorians decreed the accusation of Barère and his colleagues of the Terror, Collot d'Herbois and Billaud-Varenne, and he was sent to the Isle of Oléron. He was removed to Saintes, and then escaped to Bordeaux, where he lived in concealment for several years. In 1795 he was elected member of the Council of Five Hundred, but was not allowed to take his seat.
Later he was used as a secret agent by Napoleon I, for whom he carried on a diplomatic correspondence. On the fall of Napoleon, Barère played the part of royalist, but on the final restoration of the Bourbons in 1815 he was banished for life from France as a regicide, and then withdrew to Brussels and temporary oblivion. After the revolution of July 1830 he reappeared in France, was reduced by a series of lawsuits to extreme poverty, accepted a small pension from Louis Philippe (on whom he had heaped abuse), and died, the last survivor of the Committee of Public Safety, January 13, 1841.