In this study, GeSn nanowires (NWs) were fabricated and the thermoelectric performance in terms of power factor and contact resistance have been investigated and compared to Ge and Si. The ohmic contact to the NWs was made by Pt/Ti whereas low contact resistance was obtained by Ni-GeSn (or Ni-Ge) layers. A detailed investigation was performed to process towards low resistance Ni-GeSn phase for GeSn NWs. The phase formation of Ni-GeSn layers was examined by x-ray diffraction (XRD) and the residual strain in GeSn beneath the Ni-GeSn was also measured by high resolution reciprocal lattice mapping (HRRLM). It was demonstrated that Ni reaction with GeSn layer resulted in strain reduction in the remained GeSn material due to Ni outdiffusion to the GeSn NWs demonstrated higher Seebeck coefficient compared to Ge and Si NWs, which suggest promising thermoelectric properties in GeSn.