An adjustable shim is described for attachment to a pre-hung door or a rough opening. The adjustable shim may include a base bracket for mounting the adjustable shim to the pre-hung door or the rough opening, an inner shim, an outer shim, and a first actuator operably attached between the base bracket and the inner shim. At least one of the inner shim and the outer shim is tapered. Rotation of the first actuator translates the inner shim substantially linearly relative to the outer shim, thereby adjusting a combined height of the inner shim and the outer shim.