A foldable stroller has a frame assembly with a frame fold joint and is reconfigurable between an in-use configuration and a folded configuration. A child support structure is repositionable between a usable state on the frame assembly in the in-use configuration and an unusable state not suitable to support a child on the frame assembly. An interlock mechanism cooperates with the child support structure and is movable between a locked state preventing the frame assembly from being folded from the in-use configuration to the folded configuration and an unlocked state permitting the frame assembly to be folded. With the frame assembly in the in-use configuration and the child support structure on the frame assembly in the usable state, the interlock mechanism is retained in the locked state. The interlock mechanism is unlocked when the child support structure is moved to the unusable state.