Organisms produced through aquaculture may accumulate heavy metals in their flesh, and even low concentrations of these compounds can have significant impacts. The primary objective of this study was to analyze the heavy metal content in tilapia fish and assess its effects on gill structure and function. The fish were cultured under euryhaline conditions in the coastal waters of Poka Village, Ambon Bay, Indonesia. Water quality parameters were measured in situ, while up to 600ml of water samples were collected directly from the culture cages. A biopsy sample of 100g of tissue was taken from the fish to test for heavy metal content. Both water and tissue samples were analyzed using atomic absorption spectrometry (AAS), and bioaccumulation factors (BCF) were calculated. The results showed that the heavy metal concentrations in the cultured tilapia tissues exceeded established quality standards. For freshwater tilapia, the highest BCF values were found for zinc (Zn), followed by lead (Pb), cadmium (Cd), and copper (Cu), with values of 734.39, 400, 376.92, and 375.37, respectively. In marine tilapia, the highest BCF values were also observed for Zn, followed by Cu, Pb, and Cd, with values of 952.20, 423.38, 400, and 340.19, respectively. Gill damage was rated at 4 for freshwater tilapia and 5 for marine tilapia. These findings highlight the importance of monitoring heavy metal levels in the tissues of both freshwater and marine tilapia to safeguard human consumers.