[Show abstract][Hide abstract] ABSTRACT: Cu and Cd is trace element for most organisms including fish, but above certain limit Cu and Cd will be toxic. The present study was conducted to evaluate the toxic effect of Cu and Cd on Tilapia mossambicus via estimating the acute 96h median lethal concentration (LC 50) value. A total 120 number of Tilapia mossambicus fingerlings were subjected to 12 numbers 20-L aquaria. Fish were exposed to 0.0, 2.0, 4.0, 6.0, 8.0 and 10.0mg Cu and Cd/L for 4 days. Each dose was represented by two aquaria. Fish was daily observed and dead fish were removed immediately. The data obtained were evaluated using Behrens-Karber's Method. The 96 h LC 50 value of Cu for Tilapia mossambicus was calculated to be 6.0mg Cu/L with Behrens-Karber's Method. The 96 h LC 50 value of Cd for Tilapia mossambicus was calculated to be 4.8mg Cd/L with Behrens-Karber's Method. The behavioral changes of Tilapia mossambicus were primarily observed. It could be concluded that Tilapia mossambicus species slightly sensitive to Cu and Cd when compare both metal cadmium is more toxic than copper for the fish species.