Conventional detection methods for Listeria monocytogenes contamination in food are time-consuming and expensive, creating a need for a more inexpensive and efficient detection method. The objective of this study was to develop an inexpensive biosensor to detect L. monocytogenes in food samples. Screen-printed carbon electrode (SPCE) strips previously used by diabetic patients for glucose monitoring were modified with gold nanoparticles (AuNPs) and specific antibodies to L. monocytogenes. To facilitate detection L. monocytogenes was amplified by conjugating secondary enzyme-labeled antibodies with AuNPs. This assay has the ability to detect L. monocytogenes at 2 log CFU/g in wild blueberry samples and exhibits significant specificity over other enteric pathogens such as Escherichia coli O157:H7 and Salmonella Typhimurium. These results indicate that modifying the electrodes with AuNPs is crucial in the development and production of SPCE biosensors. The use of this optimized amperometric immuno-biosensing strip is an inexpensive, rapid method for detecting foodborne pathogens and has commercial potential.