The current study presents the energy and exergy analysis of a thermoelectric waste heat recovery system of an automobile using an aluminum-based heat exchanger. The experiment was conducted on a 4 cylinder direct injection diesel engine by varying the load with constant engine speed. Effect of second law efficiency, availability, entropy generation along with output current, and power of the thermoelectric system on various engine loads have been considered and were compared. Furthermore, the CFD analysis of the heat exchanger of a waste heat recovery system has been considered to evaluate the optimal thickness at the inlet conditions of exhaust gas. On the basis of CFD analysis, the optimal thickness of 3 mm for the heat exchanger has been used for waste heat recovery. The maximum entropy generated by the designed waste heat recovery system is found to be significantly less than the entropy generated by the engine. However, the availability of the exhaust gas is 81.8% higher than the availability of coolant. The study revealed that significant energy is lost through the exhaust, and employing higher load with constant engine speed enhances the scope of waste heat recovery.