The demand for sustainable and renewable resources has significantly increased in recent decades. Cellulose, as a potential and abundant resource in industry, offers promising prospects. As a biological polymer primarily originating from lignocellulosic biomass, cellulose is biodegradable and recyclable, making it an attractive candidate for mitigating environmental issues. In this research, microcrystalline cellulose (MCC) and cellulose nanofibers (CNFs) are modified using 1-naphthoic acid (1-NA) through an esterification reaction in a tosyl chloride/ pyridine solvent system to produce fluorophore-labeled cellulose. Various characterization methods such as Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and X-ray diffraction (XRD) are used to investigate the success of the modification reaction. Cellulose modification results in a decrease in the thermal stability of cellulose by lowering the degradation temperature. The glass-transition temperature (T g ) is observed after inducing the naphthoate side chain, which is around 160 °C. The cellulose naphthoate exhibits strong ultraviolet (UV) absorption peaks at around 282 nm and presents good fluorescence properties. Herein, it can be used in fluorescence coatings, sensors, and also packaging.