A strong Rodin influence is evident in his early work. His principal works include, “The Boy” (1885); “Cain” (1886), later destroyed; “Brotherly Love,” sometimes called “Two Friends” (1887); the allegorical “Two Natures” (1894, in the Metropolitan Museum, New York); “The Hewer” (1902, at Cairo, Illinois); “Great God Pan” Dodge Hall quadrangle, Columbia University campus, New York City; the “Rose Maiden”; the simple and graceful “Maidenhood”. In 1912 he completed several figures for the new state capitol at Harrisburg, Pa. A colossal statue of Lincoln, in 1917, was the subject of heated controversy because of its rough-hewn features and slouching stance. It is now in Manchester, England, and a replica is in Cincinnati.
The Great God Pan, one of the first works Barnard completed after his return to America, according to at least one account, was originally intended for the Dakota Apartments on Central Park West. Alfred Corning Clark, builder of the Dakota, had financed Barnard's early career; when Clark died in 1896, the Clark family presented Barnard's Two Natures to the Metropolitan Museum of Art in his memory, and the giant bronze Pan was presented to Columbia University, by Clark's son, Edward Severin Clark, 1907.
Interested in medieval art, Barnard gathered discarded fragments of Gothic architecture from French villages. He established this collection near his home in Washington Heights, New York City, in a building that he called the Cloisters. It was purchased by John D. Rockefeller Jr and forms part of the nucleus of The Cloisters collection.