A camera viewfinder accessory mounting device is disclosed for a camera viewfinder including an outwardly projecting frame surrounding a viewing window and having opposed mounting members on opposite sides of the window. The device includes a body portion having a viewing opening and cooperative mounting members for slideably engaging the opposed mounting members of the frame. The body portion includes a stop adjacent one end of the cooperative mounting members, and a catch disposed between the cooperative mounting members at another end of the cooperative mounting members and extending perpendicular thereto. The device is slideable over the camera viewfinder frame along the mounting members and the catch latches the frame to secure the device on the viewfinder.