A magazine well extension for a firearm having a magazine well and a trigger guard consists of a tapered monolithic hollow extension body closely matched to the magazine well opening. The bottom opening is larger than the top opening to more loosely receive the magazine for easier insertion. The extension is attached to the magazine well opening by upward facing rails on opposite sides at the top of the extension body which are matingly received by complimentary slots in the bottom of the magazine well. A second attachment point located at the rear of the extension includes a yoke which retains a laterally slidable captive pin that engages an outwardly extending tang on the trigger guard of the firearm. A forwardly extending lip at the front of the magazine well engages a groove on the inside wall of the extension to vertically support the extension at the front.