Abstract: Chitosan is a polysaccharide of β(1-4) linked D-glucosamine with a number of advantages such as non-toxicity, biocompatibility, and biodegradability. The control of their chemical and physical properties allows Chitosan derivatives to be used for different biomedical and industrial applications. Degree of deacetylation (DD) and polymer chain length (molecular weight, Mw) can be considered the most important features to determine the physico-chemical properties of these systems and consequently decisive factors to give desired results in formulations and applications.  Fluorescent probes have a broad range of applications in biotechnology, biology, and health research and their use is continually increasing due to their versatility, sensitivity and quantitative capabilities. In particular, fluorescent polymers have application as fotoconductive resins, photosensitive materials, electroluminescent materials, getters photon, and as biological markers. On the other hand, trimethylated chitosan derivatives have emerged in recent years for gene delivery and engineering applications. In this field, our specific interest is to develop pH probes for aberrant physiological changes. We report here the reductive amination of coumarin aldehydes with Chitosan as well as the N-acylation of Chitosan owning different DD and Mw by a coumarin derived carboxylic acid. Moreover, quaternization of the amino groups of the new chitosan derivatives that should provide water-soluble compounds has been also explored. The new solvent- and pH-dependent fluorescent polymers are characterized by HPLC-SEC, IR and NMR.