A convertible baby stroller assembly converts into a playpen as needed. The assembly includes a support having a bottom wall and a perimeter wall coupled to and extending upwardly from the bottom wall. A top edge of the support defines an access opening into an interior space of the support wherein the interior space is configured for receiving a child. A plurality of panels is coupled to the support. The panels are positionable in a deployed position wherein each of the panels extends upwardly above the top edge around the access opening defining an upper enclosure of the assembly. A frame has an upper section and a lower section. The upper section defines a handle. The support is coupled to the frame at a juncture between the upper and lower sections. A plurality of wheels is coupled to the lower section of the frame.