Fish have long been identified as good indicators for scientific studies particularly to examine heavy metal pollution in aquatic environments and its associated human health risks. This study assesses the accumulation of heavy metals in different tissues of the food fish Etroplus suratensis (Green Chromide) collected from Koggala lagoon, Sri Lanka. We quantified the concentrations of the four heavy metal ions; Cu2+, Cd3+, Pb2+, and Cr3+ across distinct tissues including skin, liver, gill, and flesh in fish in varying sizes using Atomic Absorption Spectrophotometer (AAS). Samples comprised thirty-six (n=36) fish from three different locations in the lagoon; the area near the KEPZ (L1), the middle of the lagoon (L2), and the area near the cultivation site (L3). The highest concentrations of heavy metals were found in the flesh and skin, while the lowest were observed in the gills. The range of heavy metal concentrations (g/g) in the body tissue varied by fish size; for small-sized fish, Cu (0.0443-0.6210), Cd (0.0110-0.0214), Pb (below detection level-0.46), and Cr (below detection level-39.633); for medium-sized fish, Cu (0.0713-0.6210), Cd (0.0134-0.0170), Pb (below detection level-40.906), and Cr (0.0014-0.0500) and for larger-sized fish, Cu (0.0553-0.345), Cd (0.0110-0.0256), Pb (0.0204-0.2103) and Cr (0.0194-0.0773). The levels of Cd, Cr, and Pb in the flesh tissues of E. suratensis flesh tissues were below the FAO’s recommended standards, however, the nontoxic heavy metal Cu exceeded these limits. Given the bioaccumulation and biomagnification of the studied heavy metals and the consumption of E. suratensis in the Koggala lagoon, regular monitoring is essential to ensure consumer safety.