Concentrating photovoltaic (CPV) is an alternative technique used to convert the solar energy to electrical energy. CPV is used in lieu of the photovoltaic system (PV) due to its smaller semiconductor area and consequently lower cost. The study of fluid flow and thermal characteristics for a CPV integrated with a three dimensional (3D) rectangular shaped microchannel heat sink (MCHS) is numerically investigated. Laminar and steady flow of water as a coolant is used at the present study. The flow and thermal fields are analyzed using four channel number (N) (26, 52, 78 and 104), concentration ratio (CR) from 1 to 20 and Reynolds number (Re) from 100 to 1000. The evaluating parameters such as temperature, the electrical efficiency and the electrical power are obtained from the simulation. Results show that increasing the channel number over N equals 52 leads to a slight decrease in the cell temperature while the design of 26 channels achieves less cell temperature. As the concentration ratio increases, the cell efficiency decreases due to increase of the temperature while the electrical power increases. Increasing Re provides a negligible enhancement in the cell efficiency and consequently a slight increase in the electric power.