He was a prolific and varied writer, composing more than twenty historical romances and a variety of serious historical works, including histories of Napoleon III and of the Czar Nicholas I of Russia.

He was the joint author with Ferdinand Séré of a five-volume work, Le moyen âge et la renaissance (1847), a profusely illustrated standard work on the manners, customs and dress of the Renaissance.

He also wrote many monographs on phases of the history of culture, including Manners, Custom and Dress During the Middle Ages and During the Renaissance Period.

Someone using the name Pierre Dufour published an exhaustive six-volume Histoire de la prostitution (1851–1854), which has always been attributed to Lacroix.

She lived with Paul Lacroix's collaborator, art collector Théophile Thoré-Bürger, for more than a decade until his death.