A chuck jaw changer is provided for a machine tool such as a numerically controlled lathe (22) for automatically changing the gripping jaws (32) of a quick change chuck (28) on its work spindle (26). The set of gripping jaws of the chuck are replaceably engaged in respective radial guideways (56) in a chuck body (30), with each gripping jaw being slid into and out of one guideway when that guideway is in a preassigned jaw change position on the chuck body. The chuck jaw changer has a rotary, indexing jaw magazine (34) having holder grooves (140) defined therein at constant circumferential spacings for releasably holding additional sets of gripping jaws (32') interchangeable with the jaw set on the chuck body. A jaw transfer mechanism (36) transfers a gripping jaw (32, 32') rectilinearly between that one of the guideways (56) in the chuck body which is in the jaw change position and that one of the holder grooves in the jaw magazine which is positioned in line therewith. For 9 ccurate jaw transfer a jaw guide (38) is interposed between chuck body and jaw magazine so as to provide a substantially continuous, rectilinear jaw guide track therebetween.