The thermal characteristic of nanofluid for flow in a micro-channel is reported in this study by using an array of temperature nano-sensors. In this study, K-Type Thermocouples (Chromel/Alumel) were fabricated by surface micromachining process on a silicon wafer to obtain the thin film thermocouple array (TFTA). The micro-channel with TFTA was mounted on a heater (calorimeter) for imposing a specified heat flux on the bottom surface of the micro-channel. De-ionized water (DIW) was used as the test fluid for recording the temperature profile on the wafer substrate at different flow rates and heat fluxes. Aqueous nanofluids containing alumina nanoparticles were then used to record the temperature profiles under similar heat flux and flow conditions. The temperature profile was measured with the TFTA in a linear array of 5 columns and 2 rows of sensors while the volume flow rate was varied from 5 μl/min, to 7 μl/min and to 9 μl/min. Degradation in the thermal characteristics of the nanofluid in micro-channel heat transfer was observed experimentally when the temperature exceeded a critical value. This can be explained to be due to surface fouling caused by excessive precipitation of nanoparticles.