Benjamin was a Sephardic Jewish American,a  rarity in Louisiana. His parents in 1811 sailed from England to settle in New Orleans. The mouth of the Mississippi being blockaded by the British fleet, they landed at St. Croix, where Mr. Benjamin was born. His boyhood was passed in Wilmington,  North Carolina, and in 1825 he entered Yale, but left college three years later, without receiving a degree. He then studied law in New Orleans in a notary's office, and was admitted to the bar 11 Dec., 1832. 

For some time he was engaged in teaching school, and in compiling a digest of cases decided in the local courts. This, at first only intended for his personal use, was subsequently enlarged and published as "A Digest of Reported Decisions of the Supreme Court of the late Territory of Orleans and of the Supreme Court of Louisiana" (1834). 

He soon rose to the head of his profession, and in 1840 became a member of the firm of Slidell, Benjamin & Conrad, having an extensive practice in planters' and cotton merchants' cases. He was a Whig, and in 1845 a member of the convention held to revise the constitution of the state, in which body he advocated the addition of an article requiring the governor to be a citizen born in the United States. 

In 1847 a U. S. commissioner was appointed to investigate the Spanish land titles, under which the early settlers in California claimed their property, and Benjamin was retained as counsel. On his return he was admitted to practice in the U. S. Supreme Court, and for a time much of his business was with that body at Washington. 

In 1848 he became one of the presidential electors at large from Louisiana, and was elected to the U. S. Senate in 1852, and again in 1857, but on the secession of Louisiana he withdrew from the senate, with his colleague, John Slidell, 4 Feb., 1861. Slidell was later arrested by our own Charles Wilkes, in the 'Trent Affair', which nearly resulted in another war with the British.

During his senatorial career he attained preeminence in the southern (slavery) wing of the democratic party. The abolitionist Senator Wade of Ohio referred to him as a Hebrew in Egyptian clothing'.A sharp personal controversy between himself and Jefferson Davis seemed likely to cause a duel, when the latter apologized on the floor of the senate for the harsh language he had used. Davis and Benjamin became fast friends.

He advocated the Kansas Nebraska bill of Mr. Douglas in 1854, but afterward insisted that the principle of popular sovereignty had been definitely set aside by the declaration of the supreme court in the Dred Scott case, which, he contended, should be accepted as conclusive.

"We went to bed thinking that we had ended slavery in Missouri and awoke to slavery in Illinois" - A. Lincon on the Dred Scott case.

His firm advocacy of the legal claims of slavery brought from Senator Wade, of Ohio, the remark that Mr. Benjamin was "a Hebrew with Egyptian principles." 

On the formation of the provisional government of the confederate states, he was appointed attorney general, and in August, 1861, was transferred to the war department, succeeding L. P. Walker. 

Having been accused of incompetence and neglect of duty by a committee of the confederate congress, he resigned his office, but immediately became 'secretary of state', which place he held until the final overthrow of the confederate government, despite criticism. The following resolution failed in the 'Confederate Senate' by 1 vote:

Resolved, That the Honorable Judah P. Benjamin, Secretary of State, having, in the opinion of the Senate, lost the confidence of the country as a wise and discreet cabinet minister, will subserve the public interests by retiring from the State Department. Resolved, That the Secretary of the Senate be directed to inclose copies of the foregoing resolution to President Davis and to the Honorable J. P. Benjamin.

-Resoultion of 'Senator' Wigfall

It was Benjamin who cultivated and held forth the idea of French and British intervention on behalf of the Confederacy until the bitter end. Sympathetic biographers of Benjamin refer to him as "the brains of the confederacy," , presumably meant as a compliment. It is said that Jefferson Davis was in the habit of sending to him all work that did not obviously belong to the department of some other minister. 

It was his habit to begin work at 8 A. M., and he was often occupied at his desk until 2 o'clock next morning. On the fall of the confederacy he fled front Richmond with other members of the cabinet, and, on becoming separated from the party, escaped from the coast of Florida to the Bahamas in an open boat, thence going to Nassau, and in September, 1865, reached Liverpool. He at once began the study of English law, and was entered as a student at Lincoln's Inn, 13 Jan., 1866. In the following summer he was called to the English bar, at the age of fifty-five. At first his success was slight, and he was compelled to resort to journalism for a livelihood. In 1868 he published "A Treatise on the Law of Sale of Personal Property," which is, ironically (see left), now the authority on this subject in English law (3d ed., London, 1883). 

His practice then grew rapidly, and in June, 1872, he was made queen's counsel, after which his business soon became as large and remunerative as that of any lawyer in the land. Among his many arguments, the one most generally known is that which he delivered before the court for crown cases reserved, on behalf of the captain of the "Franconia." His last great nisi prius case was that of Anson and others against the London and northwestern railway. After this he accepted only briefs upon appeal, and appeared solely before the house of lords and the privy council. Early in 1883 he was compelled by failing health to retire from practice, and a famous farewell banquet was given him in the hall of the Inner Temple, London, 30 June, 1883. He then withdrew to Paris, where his wife and daughter resided, and where his health rapidly failed until his death.