The present paper reports the numerical investigation of thermal and hydraulic performance of microchannel heat sink with hourglass profile (MCHS-HG). A 3-D conjugate heat transfer model was used to solve the problem with water as coolant and silicon as material of the heat sink. Performances of MCHS-HG were evaluated with 5 different contraction ratios, (0.2, 0.4, 0.6, 0.8 and 1.0) and 3 different aspect ratios from 4, 5 and 6 with Reynolds number in the range of 300-1800. Thermal performance of MCHS-HG was compared with microchannel heat sink with straight rectangular channel (MCHS-R). Results showed that thermal performance of MCHS-HG is better than MCHS-R for any given aspect ratio. The study on the effect of contraction ratio show that the optimum thermal performance is given by the contraction ratio of 0.4. Microchannel with narrower throat of hourglass profile gives higher pumping power. The assessment on thermal-hydraulic performance of MCHS-HG shows that the MCHS-HG is less economical to be applied as compare to MCHS-R.