Platt-Cady Mansion is a historic home located at Nichols in Tioga County, New York. The original Federal structure was constructed about 1827. It is a large two-story brick mansion, modified at a later date with a visually dominant columned portico in the Greek Revival style. Also on the property is a large two-story carriage-and-horse barn. The Cady Library has occupied the building since 1941.

It was listed on the National Register of Historic Places in 1976.