A hybrid photovoltaic-thermal (PV/T) solar air heater system which generates both electricity and heat energy simultaneously was studied. Mathematical model and test results are presented. This hybrid system consists of monocrystalline silicon cells pasted to an absorber plate with fins attached at the other side of the absorber surface. Air as heat removing fluid is made to flow through an upper channel and then under the absorber plate or lower channel of the collector. Only a small part of the absorbed solar radiation is converted to electricity, while the rest increases the temperature of the cells. Improvements to the total efficiency of the system can be achieved by the use of a double-pass collector system and fins. It gives more interesting hybrid photovoltaic-thermal system design for practical applications.