The invention of the present disclosure is that of a plumber's platform for supporting the back of a plumber or the like when replacing various plumbing fixtures under a sink, such as a kitchen or bathroom sink. In certain embodiments, a plumber's platform according to the present disclosure may be formed of a hard plastic material such as via thermoplastic molding, and may be configured with fixed or adjustable supports such as legs or feet of various types. In preferred embodiments, a plumber's platform according to the present disclosure may be configured as a lid for a toolbox of appropriate dimensions and may be affixed thereto by various means. A plumber's platform may be unitary, having legs of fixed length, or may comprise extendable or adjustable legs of the same or varying lengths. In preferred embodiments, the platform may comprise one or more tool troughs and a carrying handle cutout.