This work reports the manufacturing procedure for an impedimetric immunosensor for sensitive detection of the mycotoxin, ochratoxin A (OTA), through electroaddressing of diazonium functionalized antibodies on the working electrode of a planar Boron Doped Diamond (BDD) electrochemical microcell. The immunosensor elaboration and the immunochemical reaction between ochratoxin A and the surfacebound antibody were monitored using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The impedance variation due to the specific antibody-OTA interaction was correlated with the OTA concentration in the samples. The increase in electron-transfer resistance values presents a sigmoidal shape versus log concentration of OTA, with a dynamic range between 7 pg mL(-1) and 25 ng mL(-1). A limit of detection (LOD) of 7 pg mL(-1) and a IC50 of 1.2 ng mL(-1) were obtained. The immunosensor thus fabricated exhibited high sensitivity, good reproducibility, long-term stability, and was used for the detection of OTA in real coffee samples with a good recovery rate. The reported validated manufacturing procedure is compatible with the production of microarrays for multidetection.