Similarly to a harmonica reed, a piezoelectric MEMS cantilever is self-excited by an airflow. An airflow-induced self-excited vibration can be utilized as an energy source for energy-harvesting devices. In this study, with the aim of reducing the cut-in flow velocity, which is the lowest flow velocity required for resonant vibration, a thin MEMS structure with an intentionally warped shape was exploited in an energy harvester based on the principle of harmonica reeds. By compensating for the residual stresses of PZT and Pt electrode films, the cantilever warpage of the harvester structure can be controlled. The thin-film nature and the warped PZT/Si laminated MEMS structure enabled energy harvesting from an airflow at low flow velocities. Moreover, the cut-in flow velocity of the airflow-induced MEMS harvesting device was very low (1.2 m/s, one-tenth of that of a conventional device), and an output power of 3.84 μW was obtained at a flow velocity of 3.7 m/s.