Kirby, Petit & Green was an American architectural firm practicing in New York City, noted as the architects of Coney Island's Dreamland, among other major commissions. The three principals were architects Henry P. Kirby, John J. Petit, and James C. Green.
The firm was founded in 1902 by John J. Petit and James C. Green as Petit & Green. Petit had been practicing independently since the 1890s. In early 1903 the partnership was expanded to include Henry P. Kirby, as Kirby, Petit & Green. Kirby had served as a draftsman and designer for George B. Post, and for him designed the City College and . Green retired from the firm in late 1909, and Kirby & Petit lasted until Kirby's death in 1915. Petit practiced independently until his death.
One of the firm's significant early commissions was for the Morse High School in Bath, Maine, begun in 1902. Designed in association with William R. Miller of Lewiston, it was built in the French Renaissance style. The building burned in 1928.
Their most significant work was for the Japanese House, on Buckingham Road in Brooklyn. This was just one of many speculative houses built by developer Dean Alvord in this neighborhood. Built in 1903, it was not sold until 1906, to Dr. Frederick S. Kolle. By himself, Petit had been associated with Alvord's development since its inception in 1899.
By the time Kirby joined the firm in 1903, they had embarked on a series of corporate headquarters in New York. First was an office building and printing plant for Doubleday, Page & Company, since demolished, on East 16th Street. This was a simple Colonial Revival building. Next, in late 1904, was the Bush Terminal Building, the central office of the massive Bush Terminal operations. The new building was a small Jacobean Revival design, and was dismissed by critics as "analogous to that of a little over-dressed English lord in a gathering of rough American cow-punchers" The building, at 100 Broad Street, was replaced in 1962 by the building of the New York Clearing House Association. The last of this group, in 1906, was the American Bank Note Building, a flamboyant Beaux-Arts office building. It was described as "plain ... but imposing", with an interior of "exceeding richness". Kirby, Petit & Green also designed the plants for Bush Terminal and American Bank Note, in Brooklyn and the Bronx, respectively.