In the present work fluid flow and heat transfer characteristics of a micro pin fin heat sink were investigated both experimentally. The heat sink was fabricated from Aluminium and fitted with a polycarbonate plastic cover plate. The heat sink consist of staggered and inline arrangement of square pin fin of size 0.5mm X 0.5mm X 0.5mm. Water was employed as the working fluid subjected to heat flux 10W/cm2. The study was carried out for Reynolds number ranging 60 to 900. Later the performance of square pin fin heat sink was compared with parallel pin fin heat sink. Pressure drop, friction factor and maximum thermal resistance were employed to access the characteristic of heat sink. Significant amount of heat transfer enhancement was observed in staggered square pin fin heat sink compared to other heat sink with penalty in pressure drop.