Ochratoxin A (OTA) is a nephrotoxic and carcinogenic mycotoxin frequently found in coffee, which directly impacts human health and the economy of many countries. For this reason, there has been a growing need for simple and sensitive tools for the on-site detection of this mycotoxin. In this study, we developed a label-free impedimetric immunosensor to detect OTA. The biosensor was built on a thin-film gold electrode evaporated on glass substrtes, modified with a self-assembled cysteamine monolayer and anti-OTA antibodies. Atomic force microscopy and Microspectroscopy RAMAN confirmed the successful functionalization of the electrodes. The biosensor performance was evaluated by electrochemical impedance spectroscopy and the measurements indicated a linear relationship between the change in the impedance values and the OTA concentration in the range from 0.5 to 100 ng mL-1 with a limit of detection of 0.15 ng mL-1. The biosensor was highly selective and did not suffer matrix interference when analyzed in coffee samples. Furthermore, considering the small sample volumes, the short time required for analysis, and the possibility of miniaturization, the developed biosensor represents a promising analytical device for on-site coffee quality analyses.