In vibration-based energy harvesting, ambient vibration often occurs in such small amplitudes that it cannot be used to drive electrical generators directly. To maximize the amount of output power, the input motion is usually amplified before being used for power generation. This work presents a non-resonant piezoelectric energy harvester that relies on a compliant mechanism to amplify a given persistent input motion in order to enhance the power output. The device can be used in situations where a small cyclic relative motion occurs between two surfaces, and where a device can be fitted to extract energy. The use of a compliant mechanism, as opposed to conventional gear drives or linkages, alleviates problems of excessive clearances, friction and power losses. A finite element model is developed to investigate the effect of the various design parameters on the system performance in terms of the amplification ratio, stiffness and output voltage. Findings of the present work are verified both numerically and experimentally on a cam-driven polymer mechanism. A parametric study is conducted to investigate the most influential variables in an attempt to optimize the design parameters for maximum power output. A magnetically bistable piezoelectric beam, driven by the compliant mechanism, is finally presented and provides substantially greater amounts of output power.