An aptamer to selectively detect ochratoxin A (OTA) in cereals was developed using silver nanoparticles (AgNPs) in combination with reduced graphene oxide (rGO). As a result of characterization experiments conducted in this study, AgNPs were confirmed to be polydisperse. The electro-catalytic activity was achieved by immobilizing OTA-bovine serum albumin (OTA-BSA) on the rGO/AgNPs substrate. Based on the experimental conditions optimized for the aptasensor, the linear dynamic range was 0.002 to 0.016 mg/L and the threshold was 7×10-4 mg/L (S/N = 3). At an atomic and molecular level, computational adsorption studies revealed how the OTA-BSA interacts with the rGO/AgNPs composite substrates on a spatial scale. Calculations using density functional theory (DFT) revealed that OTA has an energy gap of-4.5 eV, which implies a strong tendency to operate as an electron donor. In addition to its excellent reproducibility and good stability, the proposed aptasensor demonstrated its applicability in the food industry.