Lead magnesium niobate-lead titanate (PMN-PT) single crystals were prepared using a modified Bridgman method and then cut into thin sheets in an [0 0 1] orientation. The sheets have chemical composition of Pb 0.995 (Mg 0.217 Nb 0.505 Ti 0.262 )O 3 and exhibit excellent ferroelectric and piezoelectric properties, in particular a high electromechanical coupling factor, providing a promising potential for the fabrication of thickness vibration mode (TVM) piezoelectric biosensors (PE-sensors). A free standing piezoelectric biodetection platform was therefore constructed from these oriented sheets by coating gold thin films as electrodes on both sides of the sheet. The resultant platform had a resonance frequency of 4.875 MHz. An equivalent circuit was modelled to further identify the piezoelectric resonant peak. Protein A was immobilized to form a bridge between the gold electrode surface and goat immunoglobulin G (IgG) probe molecules for a PE-immunosensor. The target molecules, anti-goat IgG, were applied onto the electrode of the PE-sensor, leading to a resonance frequency shift due to the added mass. The constructed PEsensor demonstrates excellent reproducibility, large dynamic range (0.1-10 g/mL) and good sensitivity (6.72 ng/Hz).