Born in Grenoble, the fourth son of a rich banker and manufacturer, Claude Périer (1742-1801), in whose house the estates of Dauphiné met in 1788. Claude Périer was one of the first directors of the Bank of France. Of his eight sons, Augustin (1773-1833), Antoine Scipion (1776-1821), Casimir Pierre and Camille (1781-1844), all distinguished themselves in industry and in politics. The family moved to Paris after the revolution of Thermidor, and Casimir joined the army of Italy in 1798.
On his fathers death he left tin army and with his brother Scipion founded a bank in Paris, the speculations of which he directed while Scipion occupied himself with its administration. He opposed the ruinous methods by which the duc de Richelieu sought to raise the war indemnity demanded by the Allies, in a pamphlet Réflexions sur le projet d'emprunt (1817), followed in the same year by Dernières réflexions in answer to an inspired article in the Moniteur.
In the same year he entered the chamber of deputies for Paris, taking his seat in the Left Centre with the moderate opposition, and making his first speech in defence of the freedom of the press. Re-elected for Paris in 1822 and 1824, and in 1827 for Paris and for Troyes, he elected to represent Troyes, and sat for that constituency until his death. Périer's violence in debate was not associated with any disloyalty to the monarchy, and he held resolutely aloof from the republican conspiracies and intrigues which prepared the way for the revolution of 1830. Under the Martignac ministry there was some prospect of a reconciliation with the court, and in January 1829 he was nominated a candidate for the presidency of the chamber; but in August with the elevation to power of Polignac the truce ceased, and on the March 15, 1830 he was one of the 221 deputies who repudiated the pretensions put forward by Charles X.
Averse by instinct and by interest to popular revolution he nevertheless sat on the provisory commission of five at the hôtel-de-ville during the days of July, but he refused to sign the declaration of Charles X's dethronement. Périer reluctantly recognized in the government of Louis Philippe the only alternative to the continuance of the Revolution; but he was no favorite with the new king, whom he scorned for his truckling to the mob.
He became president of the chamber of deputies, and sat for a few months in the cabinet, though without a portfolio. On the fall of the weak and discredited ministry of Laffitte, Casimir Périer, who had drifted more and more to the Right, was summoned to power (March 13, 1831), and in the short space of a year he restored civic order in France and re-established her credit in Europe. Paris was in a constant state of disturbance from March to September, and was only held in check by the premier's determination; the workmen's revolt at Lyon was suppressed after hard fighting; and at Grenoble, in face of the quarrels between the military and the inhabitants, Périer declined to make any concession to the townsfolk.
The minister refused to be dragged into armed intervention in favor of the revolutionary government of Warsaw, but his policy of peace did not exclude energetic demonstrations in support of French interests. He constituted France the protector of Belgium by the prompt expedition of the army of the north against the Dutch in August 1831. French influence in Italy was asserted by the audacious occupation of Ancona (February 23, 1832); and the refusal of compensation for injuries to French residents by the Portuguese government was followed by a naval demonstration at Lisbon.
Périer had undertaken the premiership with many forebodings, and overwork and anxiety prepared the way for disease. In the spring of 1832 during the cholera outbreak in Paris, he visited the hospitals in company with the duke of Orleans. He fell ill the next day of a violent fever, and died six weeks later, on May 16, 1832.
His Opinions et discours were edited by A. Lesieur (2 vols., 1838); C. Nicoullaud published in 1894 the first part (Casimir-Périer, député de l'opposition, 1817-1830) of a study of his life and policy; and his ministry is exhaustively treated by Thureau-Dangin in vols. 1. and ii. (1884) of his Histoire de la monarchie de juillet.
His elder son, Auguste Victor Laurent Casimir Périer (1811 - June 6, 1876), the father of President Jean Paul Pierre Casimir-Périer, entered the diplomatic service, being attached successively to the London, Brussels and St Petersburg embassies and in 1843 became minister plenipotentiary at Hanover. In 1846 he resigned from the service to enter the legislature as deputy for the départment of Seine, a constituency which he exchanged for Aube after the Revolution of 1848. On the establishment of the Second Empire he retired temporarily from public life, and devoted himself to economic questions or which he published a series of works, notably Les Finances et la politique (1863), dealing with the interaction of political institutions and finance. He contested Grenoble unsuccessfully in 1863 against the imperial candidate, Casimir Royer; and failed again for Aube in 1869. In 1871 he was returned by three départements to the National Assembly, and elected to sit for Aube. He was minister of the interior for a few months in 1871-1872, and his retirement deprived Thiers of one of the strongest elements in his cabinet. He also joined the short-lived ministry of May 1873. He consistently opposed all efforts in the direction of a monarchical restoration, but on the definite constitution of the republic became a life senator, declining MacMahon's invitation to form the first cabinet under the new constitution. He died in Paris on June 6, 1876.
For the family in general see E. Choulet, La Famille Casimir Périer (Grenoble, 1894).