Abstract: Background and Objective: Stem-bark of Albizia chevalieri has been used to kill fish by local fishermen over the years in some parts of Nigeria. This study investigated the effect of aqueous stem-bark extract of Albizia chevalieri on the liver and kidney of juvenile African catfish, Clarias gariepinus. Materials and Methods: Clarias gariepinus was purchased and acclimatized for 2 weeks in laboratory aquaria. An acute toxicity test was conducted with eighty fish divided into eight groups in aquaria containing ten fish each. The groups were respectively exposed to 800, 400, 200, 120, 80, 60, 40 and 0 mg L–1 of the aqueous extract of A. chevalieri to obtain the 96 hrs LC50 of 77.915 mg L–1. In the sub-acute studies, a total of 48 acclimatized fish were divided into four groups containing 12 fish in each aquarium. Group 1 served as the normal control, while groups 2-4 were respectively exposed to three sub-lethal concentrations of 19.48, 9.74 and 7.79 mg L–1 of the extract, corresponding to the 1/4th, 1/8th and 1/10th of the 96 h LC50, for 16 days. Results: The result from the serum collected every 4 days showed significant (p<0.05) increases in the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP), with significant (p<0.05) increases in the concentrations of direct bilirubin, total protein, creatinine, urea, sodium and potassium. From the acute toxicity test result, there was no survival in aquaria containing 200-800 mg L–1 of aqueous extract of A. chevalieri. Conclusion: The results showed that the death of fish on exposure to aqueous stem-bark extract of A. chevalieri could be a result of liver and kidney damages.