The random discharge of marine fish waste into the coast generates environmental pollution. However, a better valorization of these by-products leads to the extraction of sustainable biomolecules. Chitosan is a natural biopolymer that can be produced from various marine by-products, in particular the crustacean shells, crabs, and fish scales. The aim of this current study is the extraction of chitin and characterization of chitosan obtained after a deacetylation reaction from sardine scales (S. pilchardus) as a new marine source. The β form of chitin extracted undergoes deacetylation in 40 % NaOH at 121 °C for 20 min. The chemical structure of obtained chitosan was characterized based on Fourier transforms infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Scanning electron microscope (SEM), and Energy-dispersive X-ray spectroscopy (EDS). The physicochemical properties of obtained chitosan such as the ash, moisture, nitrogen, solubility, molecular weight, fat, and water-binding capacity were also determined. According to the results of FTIR and XRD analysis, the degree of deacetylation (DDA), and the crystalline index (CrI) value of obtained chitosan is respectively about 87% and 95%. The SEM and EDS analysis revealed respectively fibrillar and pleated morphology with the presence of three major elements characterizing the chitosan, which are C, O, and N. The physicochemical analysis showed that the rate of ash, moisture, and nitrogen in obtained chitosan were respectively about 0.10, 0.34, and 7%. The solubility, molecular weight, fat, and water-binding capacity of produced chitosan were found to be 93 %, 5.86 kDa, 310, and 510% respectively. Sardina pilchardus scales could be considered a promising and alternative source of chitin and chitosan, which will be applicable in a large number of fields.