Introduction. Heavy metals are an important toxic agent associated to environmental and industrial contamination that accumulate via fish and food, and are nowadays a public health issue, given their toxicity. In the upstream Chicamocha river no studies to determine mercury, copper and lead in fish have been made, even considering the serious contamination problems in the area due to an important industrial activity. Objective. This research work aims to determine the presence and the concentrations of heavy metals in the livers, gills and muscular tissues of Oreochromis niloticus (Linnaeus, 1758), a species that was brought and now is in a sector of the upstream Chicamocha river, located at the Volcan village, in Paipa. Materials and methods. Samples provided by artisanal fishermen were analyzed. The metals were determined by means of atomic absorption spectrophotometry. 12 samples from 4 specimens were assessed. Results. The highest mercury concentration was registered in livers and gills (5 μg/g) and the lowest, in muscular tissues (0,01 μg/g); as for lead and copper, the highest concentrations were 0,51μg/g in gills and 3,2 μg/g in livers, respectively. The samples did not exceed the threshold allowed by Colombian regulations and, due to the data from other studies. Conclusion. It is necessary to make wider research works in order to make a deeper characterization of the source and the cause of this contamination with metals. An identification of the population with potential of consuming these fish and establishing their representativeness in the diet of the region´s artisanal fishermen is recommended, in order to discard possible health hazards.