Generally produced by solvent sublimation via freeze-drying or critical point drying treatment, nanocellulose-based aerogels have attracted considerable interest in offering the features such as sustainability, available surface reactivity, lightweight, high porosity, and specific surface area. This study presents a novel strategy for the preparation of fluorescent aerogels based on covalent linkage between the natural skeleton of a cellulose nanofibril (CNF) and a fluorescent carbon dot (CD). The maximum CD grafting content on the CNF-based aerogel was 113 mg g–1, providing bright blue fluorescence under ultraviolet radiation with a high fluorescence quantum yield of 26.2%. Besides improved mechanical properties with a 360% increase in compression strength, the covalently bonded CD nanoparticle further serves as a structural stabilizer to endow the characteristic of shape recovery in water for the fabricated fluorescent aerogel. Finally, this aerogel displays high sensitivity and selection on the recognition of NOx and aldehyde species, which is studied for the detection of glutaraldehyde at ultralow concentrations (ppm) in water. Using the innovation of an organic solvent-free route and avoiding the toxic crosslinking reagents or fluorescent sources, the CNF/CD-based fluorescent aerogel developed in this study is a promising functional material for potential optical sensing application.