Sol-gel coatings with different amount of colloidal silica were prepared on polycarbonate substrate. The scratch resistance was measured by the pencil hardness test based on ASTM Standard D3363-00. The indentation hardness, elasticity modulus and fracture toughness of the coatings were also characterized and correlated to the observed pencil hardness. The scratch failure was found to be due to film cracking at the trailing end. Based on such an observation, the current analysis points out that the main factors towards scratch resistance are elasticity modulus, thickness and fracture toughness of the film.