High performance thermoelectric materials are required to possess multi-valley electron transport characteristics. However, this may risk causing strong inter-valley scattering and exponentially decreased carrier mobility with respect to temperature. Herein, taking indium telluride as an example, we reveal that such effects could be effectively suppressed via introducing minute antimony phases (1–2 mol%), which successfully convert the predominant scattering mechanism from inter-valley scattering to acoustic phonon scattering at high temperatures. Finally, with the noticeable improvement in both carrier mobility and power factor, a maximum zT of 0.8 is achieved in the InTe–Sb_0.01 sample at 623 K. The proposed strategy of suppressing inter-valley scattering by nano-precipitates should be one of the possible solutions to such issues.