Portraitist and genre painter John O'Brien Inman was the son of painter Henry Inman. Although his reputation has been overshadowed by that of his father, the younger Inman had a successful artistic career.

Born in 1828 in New York City, Inman studied under his father, who painted landscapes and miniatures, as well as portraits and genre scenes. By 1853, the younger Inman was exhibiting at the National Academy of Design. In his youth, he worked as a portrait painter in the South and West; later he moved his studio to New York City, where he specialized in small genre pieces and flower paintings. Inman was elected an associate of the National Academy of Design in 1865. The following year, he moved to Europe and opened a studio in Rome. He remained abroad until 1878, when he returned for a while to New York. While in Europe, he executed a number of sentimental genre scenes with local settings.

He died in Fordham, New York, in 1896.