Caïn was born in Paris, and studied under Rude, Guionnet, and Pierre-Jules Mêne (whose daughter he married in 1852). His first exhibit in the Salon of 1846 was a wax model of a linnet defending her nest from a rat, later cast in bronze and shown at the 1855 Salon. Between 1846-1888, Caïn exhibited 38 models at the Salon.
From 1868 onwards he concentrated on monuments, including the Chiens de meute at the Château de Chantilly, Le Lion de Nubie et sa proie in the Jardin du Luxembourg, and Tigress and Peacock in the Gardens of the Tuileries. In 1879 he assumed management of his father-in-law's foundry upon Mêne's death.