Zearalenone (ZEN) is a highly toxic mycotoxin produced as a secondary metabolite by various Fusarium species. To detect this contaminant in cereal products, we developed a quartz crystal microbalance (QCM)–based aptasensor. To amplify the sensor signal, an electrochemically deposited diazonium-derived film was formed on the crystal surface, and gold nanoparticles were subsequently decorated on this film to facilitate aptamer immobilization. All materials and modified surfaces used during sensor fabrication were thoroughly characterized by UV–vis. spectroscopy, transmission electron microscopy, cyclic voltammetry, and X-ray photoelectron spectroscopy. Under optimized conditions, the QCM aptasensor exhibited a linear detection range of 0.1–250 ng/mL for ZEN, with a limit of detection of 0.182 ng/mL. Its selectivity was evaluated against potential interferents, including ochratoxin A and B and aflatoxin B1, and interference effects remained within acceptable reproducibility limits. Kinetic analysis demonstrated a surface-confined, mass-transfer-limited interaction, as evidenced by the pseudo-second-order kinetic fit and the increasing Kd values at higher ZEN concentrations, yielding an average dissociation constant of 128 ± 153 ng/mL. Finally, the aptasensor successfully quantified ZEN in spiked wheat and corn samples, yielding recoveries between 95 % and 105 %.