Aflatoxin B1 (AFB1) is a highly toxic and carcinogenic mycotoxin with high health risk due to its widespread food contamination. This study investigates a pyrrole-based single-molecule junction with graphene electrodes for amperometric sensing of AFB1, to address the need for for rapid, sensitive, and field-deployable detection of AFB1. Density Functional Theory (DFT) simulations are employed to study the adsorption process of AFB1 on the polypyrrole molecular junction and its influence on the electronic transport properties. Structural optimization confirms that AFB1 binds stably to the polypyrrole which triggers charge redistribution within the system. This molecular attachment affects the conductive properties of the sensor, as reflected in its current-voltage (I-V) characteristics.