[en] Highlights: ► Thermo-mechanical treatments and C addition improved the mechanical and electrical properties. ► The difference of properties was affected by the Fe precipitates phases and sizes. ► The Fe₃P particles were only marginally affected by the final processes. - Abstract: The microstructures, secondary-phase particles and precipitates of thermo-mechanically treated non C-alloyed and 0.0133 wt.% C-alloyed Cu–2.5Fe–0.1P alloys were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). All of the thermo-mechanical treatment processes consequentially improved the mechanical and electrical properties. The Fe₃P particles were only marginally affected by the final processes. The Fe precipitates, by contrast, showed different phases and sizes resulting from C-alloying and the final processes; thus, the mechanical and electrical property changes manifested in the alloys were attributed to the Fe precipitates.