Fluorine toxicity has negative effects on soft tissue besides skeletal and dental tissues. In the present study, we have investigated the protective effect of chitosan (CS) and chitosan oligosaccharide (COS) on liver tissue of fluorine-intoxicated rats taking the antioxidant characteristics of chitosan and its derivatives into consideration. In this study, 42 male Wistar albino rats were randomly selected to determine the control and experimental fluorosis groups. Our study lasted for 12 weeks. As a consequence of the study, MDA significantly increased in the liver tissue of NaF group while some antioxidant values significantly decreased. It was detected that serum AST and LDH levels increased significantly while ALB and TP values significantly decreased in NaF group. The degenerations were identified in the liver histopathology of all fluoride- treated groups. We have concluded according to the results that chitosan oligosaccharide can be more effective compared with chitosan.