Doubts about the authenticity have long surrounded In Central Park. Eugénie Prendergast, the sister-in-law of Maurice Prendergast and heir to the Prendergast brothers, questioned the work in the 1970s. Scholars have noted both the absence of Prendergast's typical tapestry-like effect in the brushstrokes and a crudity to the figures that resembles a fake Prendergast gouache withdrawn from an auction in the early 1980s.

When the museum became the repository for the Prendergast collection and archives, work on the book documenting all known works by Maurice Prendergast (the catalogue raisonné) was begun. The team working on the project issued the authoritative opinion that the painting is not by Prendergast. They noted that the work is a pastiche of elements from known Prendergast paintings. The composition is largely derived from Central Park, a painting in the collection of The Metropolitan Museum of Art since 1950. But the forged painting also contains figures copied from at least one other authentic Prendergast: the kneeling figures in the foreground and the two figures on the far left are lifted from a 1918 work, On the Beach, No. 3. This painting was illustrated in color in the 1960 catalog to the exhibition Maurice Prendergast, 1859-1924 held at the Museum of Fine Arts, Boston. Mid-twentieth-century forgers often used exhibition catalogs with their detailed color plates for piecing together spurious compositions with design elements copied from various authentic paintings. Once this painting was no longer considered to be a Maurice Prendergast, it was given to WCMA for teaching purposes.