This paper introduces a creative metamaterial-based substrate (MetaSub) for piezoelectric energy harvesters. The MetaSub is a platform with a high flexibility in both longitudinal and transverse directions. The novel design of the MetaSub remarkably improves the productivity of strain-induced devices in structural health monitoring (SHM) applications, internet of thing (IoT) networks, micro electromechanical (MEMS) systems, vibration energy harvesters, sensor and actuators, and hundreds applications that its performance is related to their deformation capability. In this paper, a piezoelectric type of energy harvester is selected to be studied numerically as the first application of the MetaSub. The finite element results predict the average power output gained by the MetaSub piezoelectric energy harvester to be up to 19.2 times more than power generated by an equivalent conventional piezoelectric energy harvester.