The present study aims to investigate the performance of a thermoelectric generator (TEG) under the influence of sinusoidal temperature distribution at the hot side or cold side surface. The impacts of the period and amplitude of the periodic temperature, the temperature difference between the two surfaces, and the external load resistance on the power output and efficiency of the TEG are studied. The numerical simulations indicate that the period of temperature fluctuation plays no part on the TEG performance, whereas the power output of the TEG is significantly affected by the oscillating temperature. The higher the temperature amplitude, the larger the power output. With the temperature amplitude of 75 K at the hot side surface, the power output can be intensified up to 18%. In contrast, the maximum improvement in the power output is less than 1% when the oscillating temperature is excited at the cold side surface with the temperature amplitude of 15 K. The predictions also suggest that the optimal external load resistance is not affected by the boundary conditions of oscillating temperature, and the TEG performance is identical when the temperature difference between the two surfaces is fixed. (C) 2017 Elsevier Ltd. All rights reserved.