In folklore medicine, Ceriops decandra is used to treat hepatitis. However, a scientific evaluation has not been performed. Thus, the present study was carried out to identify the hepatoprotective activity of plant parts (leaf, bark, collar, flower and hypocotyls) of C. decandra. In vitro antioxidant studies were carried out with DPPH, HRSA, NO, FRAP and LPO assays. The LD 50 was calculated and in vivo hepatoprotective activity was carried out with the leaf extract, which was found to be the most potent. The in vivo hepatoprotective activity was performed as follows: Group 1, control animals; Group 2, carbon tetrachloride (CCl 4)-treated animals; Group 3, silymarin (100 mg kg −1 bw p.o.) treated animals; Groups 4, 5 and 6, C. decandra treatment groups (100, 200 and 400 mg kg −1 bw). Histopathological scores were calculated with standard protocols. Of the selected different plant parts, the leaf extract showed maximum antioxidant scavenging properties. A study of the oral acute toxicity found C. decandra extract to be non-toxic up to 2000 mg kg −1 bw. The in vivo hepatoprotective nature of the leaf extract was identified as dose dependent and the levels of SGOT, SGPT, ALP, bilirubin, CHL and LDH were found to be significantly decreased (p < 0.05) compared with hepatotoxin groups. Histopathological scores did not show any significant variations between control and high dose (400 mg kg −1 bw) of leaf extract-treated animals. Preliminary phytochemical analysis of the leaf extract revealed the presence of phenolic groups, alkaloids, triterpenoids, flavonoids, catechin and anthraquinone. In conclusion, the hepatoprotective nature of the C. decandra leaf extract might be due to the occurrence of unique secondary metabolites and their antioxidant scavenging properties.