The present research determined the total mercury concentrations in muscle and liver tissue in fish collected from the Magdalena River watershed. A total of 378 muscle samples and 102 liver samples were included in the analysis. The highest mean mercury level in muscle tissue was found in the noncarnivore, Pimelodus blochii. However, as a group, carnivores had significantly higher (p < 0.05) mercury levels in their muscle tissue than noncarnivores. A significant correlation (p < 0.05) was obtained between fish mass and mercury concentrations in muscle or liver in four species. No differences were observed in total mercury concentration based either on species or gender.