Mechanical biocompatibility, including tensile properties and Young's modulus, of β-type Ti-Mn alloys, namely, Ti-10Mn and Ti-14Mn, fabricated by the metal injection molding method were investigated. The bone formability (biological biocompatibility) of a Ti-Mn alloy, namely, Ti-12Mn, fabricated by the arc-melting method was evaluated by means of an animal test. The tensile strength of sintered Ti-10Mn and Ti-14Mn achieve a maximum value of 860 and 886 MPa, respectively. The Ti-14Mn specimen sintered at 1273 K shows the lowest Young's modulus (76 GPa) among all sintered Ti-10Mn and Ti-14Mn specimens. The tensile strength of Ti-Mn alloys is almost equal to that of Ti64 ELI; further, their Young's modulus is lower than that of Ti-6Al-4V ELI. The relative bone contact ratio of Ti-12Mn increases from 11% to 29% with increasing implantation time from 12 weeks to 52 weeks. Moreover, the relative bone contact ratio of Ti-12Mn and CP-Ti is almost constant for all implantation times.