Abstract. Musa Estuary is receives various type of discharges such as petrochemical, industrial and urban waste, it also is a habitat for Johnius belangerii. This study was carried out to determine heavy metal concentrations in J. belangerii. Fish samples were taken from 5 creeks and acid digested for their heavy metal contents. Results showed that the highest level of Cd, Co, Cu, Ni and Pb was 7.21, 1.08, 1.12, 2.72 and 4.57 in liver, 1.88, 1.04, 2.09, 9.43 and 6.83 in gill and 0.14, ND, 5.61, 2.43 and 3.78 in muscle respectively. The level of heavy metals in muscle was lower than WHO standard, however the level of metals in fish were decreased by the increase of distance from PETZON. It is suggested that biomonitoring of contaminants in this estuary could serve as a good estimate of environmental health