Fish gills were evaluated in this study as potential target organ for accumulation of heavy metals. Pollution has become a hydra-headed problem which is aggravated daily especially in the developing countries where effective waste management and pollution control are hardly established. In the aquatic environment, several objects, both living and non-living have been studied for use as indicators of water pollution. Two species of fish, tilapia (Tilapia zilli) and cat fish (Chrysichthys nigrodigatatus ), were studied for heavy metal levels in the gills and the fillet. Samples were taken from Ikorodu lagoon in Lagos state, Nigeria. The samples were oven-dried, digested and analyzed using atomic absorption spectrophotometer. The values of heavy metals in the gills of cat fish ranged from 1.08-2.2 mg/kg for Zn; 1.19-2.66 mg/kg, Cu; 5.105-10.56 mg/kg, Pb; ND-10.715 mg/kg, Fe; and 0.66-1.67 mg/kg, Cd. The levels obtained in the fillet of cat fish were 0.787-1.045 mg/kg for Zn; 0.312-1.045 mg/kg, Cu; ND-3.22 mg/kg, Pb; ND-20.102 mg/kg, Fe; and ND-0.777 mg/kg, Cd. For heavy metal levels in tilapia samples, the levels in gills ranged from 1.135-4.07 mg/kg for Zn; 1.11-2.66 mg/kg, Cu; ND-2.102 mg/kg, Pb; 69.105-122.28 mg/kg, Fe; and ND-1.52 mg/kg, Cd. The levels in the fillet of tilapia fish were 0.735-1.585 mg/kg, Zn; 0.752-2.697 mg/kg, Cu; ND-0.392 mg/kg, Pb; 19.572-125.217 mg/kg, Fe; and ND-0.947 mg/kg, Cd. The gill/fillet heavy metal accumulation ratios were all greater than 1, except for Fe in catfish and Cd in tilapia. It could be inferred from this study and the reviewed literatures that fish gill was a potential target organ for accumulation of heavy metals. And this could be due to constant contact of gill blood stream with heavy metal polluted water in the process of inflow and outflow of water through the gills.