A paint roller tray mounting device includes a platform that has a width sized to fit between first and second side rung supports of a ladder, a length sufficient to support a paint roller tray. The platform has a recess in an upper surface sized and shaped to provide a gripping surface for a ladder rung. At least two securing hooks have a hooking end and an attaching end. The hooks are symmetrically attached at the attaching end adjacent opposite edges of the platform. The hooks extend from at least a lower surface of the platform to a surrounding upper edge of the paint roller tray. The hooks have a tightening device for urging the tray and the platform together. The platform is located beneath the ladder rung or a top shelf of a step ladder. The paint roller tray is located above either the rung or the top shelf.