This paper deals with the dynamics of flow in a zig-zag square microchannel subjected to uniform external heat flux (H2 thermal boundary condition). The heat transfer and fluid flow characteristics is studied using CoventorWare™. Numerical studies are performed using microchannels with hydraulic diameter ranging from 100 μm to 300 μm for Reynolds number between 25 and 500. The angle which each arm of the zig-azg microchannel makes with the axial direction is varied from between 10° and 30° with increments of 10°. The effect of number of turns in a repeating unit for a specific length of the microchannel is also investigated in this paper. The Nusselt number and Poiseuille number in a zig-zag microchannel is found to be totally different from that in a straight square microchannel of the same geometric dimensions. These two parameters are found to increase with increase in Re for zig-zag microchannels with fixed geometry. The individual effect of each of these parameters is to increase both Nusselt number and Poiseuille number for a specific Reynolds number. The enhancement is highest with increase in number of turns while it is the lowest with increase in hydraulic diameter. The enhancement in Nusselt number and Poiseuille number is explained using the flow profile in the microchannels.