Legionella pneumophila is a significant public health threat, responsible for severe diseases such as Legionnaires’ disease. Traditional detection methods are often labour-intensive, time-consuming, and require sophisticated equipment. This study introduces smart fluorogenic polymeric materials for the naked-eye detection of L. pneumophila via protease activity. These materials, prepared as hydrophilic films, cellulose-coated linear co- polymers, and electrospun nanofibers, operate on an OFF/ON FRET system, emitting fluorescence under UV light upon interaction with L. pneumophila proteases. Characterisation confirmed the successful immobilisation of the peptide substrate and its response to proteases. The sensors showed moderate to high sensitivity and specificity, with detection limits of 2.91 × 105, 3.64 × 10⁵, and 4.04 × 105 CFUs/mL for the film, copolymer, and nanofiber formats, respectively. Cross-reactivity tests identified only Pseudomonas aeruginosa as an interferent. This novel approach offers rapid, simple, and cost-effective L. pneumophila detection with visible results under UV light, suitable for clinical and environmental samples. It highlights the potential for broader pathogen detection applications.