After a distinguished legal career in Nîmes, he was appointed advocate of the Court of Appeals in Paris (1830), where he gained further renown for his legal skill and oratory.

In 1842 Crémieux was elected to the Chamber of Deputies from the Indre-et-Loire département and quickly emerged as a leading member of the radical left. He played a prominent role in the revolutionary movements of 1848 and served as minister of justice in the provisional government of 1848–49. He voted for the presidential candidacy of Louis-Napoléon, but, when he withdrew his support, he was imprisoned. After his release, he returned to the bar and left-wing politics. He returned to the Chamber in 1869, representing a Parisian district, and, when the Second Empire collapsed, he joined the Government of National Defense (1870–71) as minister of justice. Subsequently, he served as a deputy from Algiers (1871–75) and then senator (1875–80).

Crémieux was an important leader of the French Jewish community. He lent his prestige and political influence to numerous campaigns for the normalization of Jewish life in France and Algeria, backing the enfranchisement of North African Jews. He was a founder of the influential Universal Israelite Alliance and was its president from 1863 to 1880.