Abstract: A floor lock assembly for a playpen prevents collapse of the apparatus when it is occupied by a child, whereby a potential safety problem is obviated. In a typical playpen collapsible frame, a lower frame assembly is comprised of a pair of parallel connecting rod units pivotally joined to a pair of crossing rod assemblies. The floor lock assembly extends between the pivoting intersections of the crossing rod units, and includes a pair of rigid linking members extending in opposed relationship from a lock bracket, each linking member pivotally joined to one of the pivoting intersections of the crossing rod units. Each linking member is limited in angular range in its pivoting relationship to the lock bracket, whereby the lock bracket may be supported by the linking members (when the lower frame is in a deployed configuration) in a generally horizontal overcenter disposition beneath a medial portion of the floor panel of the playpen.