A microelectromechanical systems piezoelectric transducer capable of measuring static accelerations and acoustic vibrations has been designed and proposed. The transducer is composed of a circular plate on a pillar, which is fixed at the centre and free at the rim so that it resembles a flat cap mushroom. An annular piezoelectric layer has been employed to convert the vibration-induced stress of the plate to a potential difference. The proposed structure has been compared with diaphragm piezoelectric transducers and hydrophones and its superior performance has been verified. Analytical models for both static and dynamic accelerations have been developed, discussed and the output voltage has been formulated, which is in a very good agreement with the finite element analysis. Results show that the maximum sensitivity is achieved when there is an annular piezoelectric layer on the plate around the pillar perimeter. The effect of different geometrical parameters on the transducer performance has been studied. The proposed flat cap mushroom shape piezoelectric transducer could achieve −186.5 dB sensitivity and a very wide bandwidth. Another important advantage of the proposed structure is that by controlling the pillar radius and without changing the plate size, the sensitivity can be enhanced.