Since the maximum shape recovery temperature of the binary Ti-Ni alloys is limited to be around 400K, the increase in martensitic transformation temperature (M
s) of Ti-Ni should be done by alloying for the demand of high temperature applications. Although most of additional elements are known to decrease M
s of Ti-Ni, substitutional elements having large atomic size are expected to increase M
s. In this study, phase constitution, phase transformation temperature, lattice parameter of B2 phase and Vickers hardness were investigated for Ti-Ni alloys containing several platinum-group metals (PGM). The alloy systems investigated were the pseudobinary systems of TiNi-TiRh, TiNi-TiIr and TiNi-TiPt where the PGM atoms substitute for the Ni-sites of TiNi. The phase transformation and phase constitution were assessed by differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). It was found by XRD that TiNi can contain a large amount of the PGMs as Ti(Ni, Rh), Ti(Ni, Ir) and Ti(Ni, Pt). Lattice parameters monotonously increase with increasing amount of PGMs. With increasing Pt content, M
s slightly decreases when less than 10mol%Pt while continuously increases as the rate of 26K/mol%Pt when more than 10mol%Pt. On the other hand, M
s decreases and then disappears with increasing Rh or Ir content. Hardness ranges from HV180 to HV570 and the maximum values in the pseudobinary systems lie around 20–30mol%PGM, suggesting solid solution hardening caused by the substitution of PGMs.