Heat sinks that cool electronic systems through flow boiling are exposed to working fluids at different inlet temperature. Therefore, in the present study, influence of inlet temperature on boiling performance of a micro-pin-fin-type heat sink with expanding cross-sectional area is experimentally investigated. The analysis is supported by comparing the results with those obtained via a plain-wall (conventional) heat sink. The experimental range covers two heat sinks (HS − 1: Conventional; HS-2: Expanding pin-fin-type), two values of mass flux (G = 120 and 190 kg m−2 s−1), three inlet temperatures (Ti = 25 °C, 45 °C, 65 °C) and five values of heating power (170 W – 210 W with 10 W increments). It is concluded that inlet temperature is an influential parameter for thermal characteristics as well as values of pressure drop. A remarkable increase is obtained for heat transfer coefficient with decreasing inlet temperature for HS-2. When a decrease occurs from Ti = 65 °C to Ti = 25 °C, heat transfer coefficient increases between 94.7%–620.8% for HS-2 at G = 190 kg m−2 s−1. HS-2 increases heat transfer coefficient up to 841.3% compared those of HS-1. Regarding both HS-1 and HS-2, a decrease in inlet temperature also leads a decrease in pressure drop for a given heat flux.