A ready-to-assemble mattress foundation including a plurality of rails forming a mattress foundation having a plurality of corners. The mattress foundation includes a plurality of corner connector assemblies coupling the rails together at the corners. Each of the corner connector assemblies includes a first corner bracket; a second corner bracket; a pin including internal threads and external threads; and a fastener threadably engaging the external threads of the pin to retain the pin relative to the corner brackets. The pin extends through the first apertures and the second apertures. The mattress foundation includes a plurality of central support assemblies coupled to one or more of the rails. Each of the central support assemblies includes a body having internal threads. The mattress foundation includes a plurality of legs each including a threaded rod and threadably received within the internal threads of the pin and the central support assemblies.