Efficient cooling of high heat flux devices has promoted the development of micro pin fin heat sinks. In this study, four micro pin fin heat sinks (MPFHSs) with different pin fin shapes, i.e., circular, square and diamond and streamline ones are fabricated by laser micromilling methods. Their single-phase heat transfer and fluid flow performance are explored to assess the pin fin shape effect. Convective flow tests are conducted at Reynolds number of 150-750 at two heat fluxes using deionized water as the coolants. It was found that the streamline MPFHS presented the best heat transfer performance. On the contrary, the diamond fin pin heat sink presented the worst heat transfer performance, whereas it featured the smallest pressure drop among the four MPFHSs. The diamond micro pin fins showed the smallest thermal resistance at a certain pressure drop, and should be selected as the optimum one for the MPFHS applications when the overall thermal and hydraulic performance is considered.