In this study, we report a piezoelectric energy harvester adopting a fishtail bluff body (FTEH) to scavenge ambient wind energy. The biomimetic nature of the FTEH contributes to enhancing the harvester's performance. This enhancement stems from the geometric variations of the fishtail bluff body, which undergoes undulation during fluid–structure interactions, thereby affecting the dynamic behavior of the harvester. An electromechanical coupling model has been developed to explain this phenomenon. Experiments were conducted to evaluate the energy-harnessing performance of harvesters equipped with three distinct bluff bodies. The results demonstrate that the FTEH exhibits outstanding performance compared to traditional energy harvesters utilizing cuboid bluff bodies after the threshold wind speed. Specifically, under the excitation of airflow at a speed of 23 m/s, the RMS voltage for the fishtail structure, about 3.24 V, surpasses the corresponding voltage for the cuboid-L bluff body (0.73 V) to approximately 440% and that for the cuboid-S bluff body (0.40 V) to approximately 810%. Moreover, the charging capability, for a 100 μF capacitor, of the FTEH is around 60 and 110 times greater than that for those cuboid bluff bodies, respectively. This study holds significant implications for the development of self-powered systems in windy environments.