Abstract: There is provided a ladder tray for supporting tools or materials on a ladder that includes a receptacle defined by a bottom surface, a first transverse side, a second transverse side, a first longitudinal side, and a second longitudinal side in which the four sides extend upward from the bottom surface. The first transverse side includes a support member for mounting onto a step or horizontal surface of a ladder, such as a step ladder or an extension ladder. The first transverse side also includes a width guide for engaging the uprights of the ladder to prevent longitudinal and transverse motion of the mounted ladder tray. The ladder tray also includes an opening through the first transverse side for receiving a protrusion from a ladder. Flanges may be included on the longitudinal sides which define orifices for supporting tools and materials, and dividers may be included within the receptacle to define compartments within the receptacle.