A folding mattress support system replaces both a conventional box spring and the bed frame with rails. The mattress support system is lighter, quieter and easier to transport, and also provides more storage space beneath the mattress. The mattress support system includes bed frame assemblies, central connecting bars, edge attachments and a bed skirt. Leg brackets fold out from the bed frame assemblies, which themselves unfold in the middle. Central connecting bars connect inner side edges of the bed frame assemblies. Plastic edge attachments are attached at outer corners of the bed frame assemblies and hold a bed skirt taught around the frame assemblies when the frame assemblies are standing on the extended leg brackets. A mattress is then placed on top of the assembled mattress support system. Optionally, metal edge attachments at the head corners of the mattress support system both hold the bed skirt and support a headboard.