This paper presents the characteristics of Mo-based (Mo-Zr based) amorphous alloys exhibiting a high crystallization temperature. In order to investigate the alloy composition showing an amorphous state in the Mo-Zr-X (X=Si and Al) alloy system, thin film libraries were prepared at first by combinatorial arc plasma deposition (CAPD). The composition region corresponding to the amorphous state was identified in the libraries with X-ray diffraction. On the basis of the alloy composition and phase distribution of the thin film libraries, additional amorphous Mo-Zr-Si and Mo-Zr-Al thin films were prepared by a carousel sputtering system. The crystallization temperature Tc of the amorphous Mo50Zr(50-x)Six thin films exceeded 1073 K. However, the Mo-Zr-Si thin films were so brittle that they could not be subjected to tensile testing. In the Mo-Zr-Al thin films, Tc of the Mo-rich MoxZr(90-x)Al10 and MoxZr(76-x)Al24 thin films exceeded 973 K. Although the toughness of Mo-based amorphous alloy thin films could be improved slightly by adding Al, the amorphous Mo-Zr-Al thin films were also brittle.