A foldable baby stroller frame comprises a collapsible wheeled frame, a foldable upper frame, and at least a release mechanism. The collapsible wheeled frame comprises at least a front strut, a pair of rear struts, a pair of lockable articulated arms, and a swivel base. The swivel base is pivotally connected with the front strut and the rear strut, and further has a vertical shaft hole for pivotally connecting and supporting the foldable upper frame. The pair of lockable articulated arms is pivotally connected between the front strut and the rear strut, and has a locked position for keeping the collapsible wheeled frame in an un-foldable state and a foldable position for folding the collapsible wheeled frame. The release mechanism is operatively mounted on the foldable upper frame and associates with the pair of lockable articulated arms via a connecting member for actuating the folding of the collapsible wheeled frame and the foldable upper frame.