In Zambia, the rising demand for fish as a vital source of animal protein has increased demand for fish from both aquaculture and wild fisheries. However, increasing pollution from agricultural, mining, and domestic sources has been driven heavy metal accumulation in aquatic environments, threatening public health and the future of aquaculture. This study quantified eight heavy metals: Cadmium (Cd), Cobalt (Co), Copper (Cu), Iron (Fe), Manganese (Mn), Nickel (Ni), Lead (Pb), and Zinc (Zn) in the muscle, liver, kidney, and gills of Nile Tilapia (Oreochromis niloticus) from five sites in Lake Itezhi-Tezhi using atomic absorption spectrophotometry. Two-Way ANOVA revealed significant variations (p < 0.05) in metal concentrations across sites and organs, as well as their combined effect. The liver and kidney consistently showed the highest metal burdens, followed by gills and then muscle. Principal Component Analysis (PCA) clearly differentiated metal accumulation patterns by site and organ, indicating localised contamination sources. Critically, lead concentrations in fish muscle reached 1.39 mg/kg dw at Nachisenga, and cadmium levels were as high as 0.86 mg/kg dw at the same site, both exceeding the FAO/WHO and EU maximum permissible limits of 0.5 mg/kg dw and 0.05 mg/kg dw respectively. These elevated levels of toxic metals in edible tissues pose a serious risk to human health, especially for populations that consume fish regularly. Moreover, the contamination threatens the sustainability of aquaculture, as the same waterbody supplies broodstock for tilapia and supports downstream aquaculture operations, potentially compromising fish health and food safety. These findings underscore the urgent need for routine environmental monitoring and stricter pollution control measures to protect public health and ensure the long-term viability of aquaculture practices in Zambia.