An anti-walk pin assembly for securing a fire control group having a trigger, disconnector and hammer within a firearm. A lower receiver defines a fire control group receptacle for housing fire control group components. The lower receiver has trigger pin receiving openings each defining a trigger pin support surface. A trigger pin is received in the trigger pin receiving openings. The trigger and disconnector are pivotally mounted on the trigger pin. A threaded fastener engages with a threaded portion of the trigger pin support surface to restrict lateral movement of the trigger pin within the trigger pin receiving openings. Further optionally included are hammer pin receiving openings each defining a hammer pin support surface. A hammer pin is received in the hammer pin receiving openings. A threaded hammer fastener engages with a threaded portion of the hammer pin support surface to restrict lateral movement of the hammer pin.