In this study titanium-zirconium-molybdenum alloys (Ti 50 Zr 50 ) 100-x Mo x (xMo; x = 0 at.%, 1 at.%, 3 at.%, 5 at.% or 7 at.%) were investigated, focusing on the effect of molybdenum addition on their microstructures and mechanical properties. Transmission electron microscopy observations revealed that the binary Ti 50 Zr 50 alloy was composed entirely of an acicular hexagonal structure of the a' phase. When the molybdenum content was 1 at.%, the alloy was composed of b and w phases. However, when 3 at.% or more molybdenum was added, only the equiaxed, retained b phase was observed. Tensile tests at room temperature indicated that the mechanical properties of the 1Mo alloy were inferior owing to the embrittlement effects of the w phase and the difficulty of dislocation motion through the w phase. Our research suggested that the 5Mo alloy had excellent ductility (16.5 %) as well as adequate strength (780 MPa). The improved mechanical properties were attributed to the enhanced stability of the b phase and the disappearance of the w phase.