The potential of a conductimetric immunosensor to detect residual amounts of atrazine in a complex matrix, such as red wine, is evaluated. The immunosensor presented is based on interdigitated μ-electrodes (IDμEs), immunoreagents specifically developed to detect atrazine, and antibodies labelled with gold nanoparticles. Due to the amplification of the conductive signal, produced by the presence of the gold particles, atrazine can be detected using simple and inexpensive direct current (DC) measurements. Then, sensors response is related to the atrazine concentration in the sample. Likewise, the presence of gold particles generates an increase in the intensity of the electric field between the electrodes. The time for assay completion, for 48 samples, was 5 h. Nevertheless, during the first hour (devoted to the incubation assays), the number of samples could be increased without prejudice the assay duration. Sensor responses obtained using red wine samples are compared with results obtained using buffer solutions. As a consequence, the strong matrix effect related to red wine samples has been identified as a non-specific increase of the current intensity through the device. The limits of detection (LODs) obtained are far below the Maximum Residue Level (50 μg kg −1) established by EU for residues of atrazine as herbicide in the wine grapes and other foodstuff products. This opens the door to commercial sensors of simple manipulation, transportable and economics.