A spare magazine holder for a holster facilitates rapid magazine replacement. Each spare magazine is supported in a well in the holder at a predetermined angle relative to the grip of the pistol in the pistol sleeve to allow for straightforward and rapid exchange. The spare magazine may be substantially parallel or at least near-parallel to the magazine loaded in the grip of the pistol in the pistol sleeve. The holder preferably includes two wells in a vertical stack, each configured to receive a spare magazine at substantially the same angle. One or more fasteners may be provided for adjusting the frictional engagement of the spare magazine disposed in each well. The spare magazine(s) may be disposed in a plane parallel to the plane of the pistol, and this plane may be offset from the plane defined by the grip and the barrel of the gun.