Imidacloprid is the most widely used insecticide in agriculture and its intensive use over the last 30 years has caused a global concern due to its potentially toxic effects on the ecosystem. Considering the recent scientific interest in novel simple methods for imidacloprid analysis, we propose a label-free sensitive and specific localised surface plasmon resonance system for the detection of the insecticide based on 2D nanostructured metasurfaces with highly performing plasmonic properties. The specificity of the sensor proposed was achieved by covalent bio-functionalization of the metasurface using a smart and easy one-step procedure mediated by carbon disulphide. The biosensor produced was tested using a set of imidacloprid standard solutions showing a competitive limit of detection, lower than 1 ng mL-1. Our novel nanosensing configuration represents a valid and reliable solution to realize low-cost portable POC tests as an alternative to the laborious and expensive methods traditionally used for insecticide detection.