Concentrations of the heavy metals cadmium (Cd), mercury (Hg), nickel (Ni), lead (Pb), chromium (Cr), copper (Cu) and zinc (Zn) in adult banana prawns (Fenneropenaeus merguiensis de Man, 1888) were determined. Banana prawn samples were collected from two provinces of Thailand (Ampur LamSing, Chantaburi, and Ban Huanumkao, Trat) by gill net. Twenty five prawns from each province were randomly chosen from the catch and each prawn sample was divided into two parts: cephalothorax and abdominal muscle. Both parts were digested with concentrated nitric acid and hydrogen peroxide under pressure in a microwave digester. Hg levels were determined using a Cold Vapor Atomic Fluorescence Spectrometer. Cd, Cu, Cr, Ni, Pb, and Zn concentrations were determined using Atomic Absorption Spectrophotometer. Trace concentrations of Cd, Cu, Cr, Ni, Pb, and Zn in cephalothorax of banana prawns from both provinces were significantly higher (P < 0.05) than in muscle, with no significant difference observed for Hg. Concentrations of Hg, Cu, Zn, and Cd in banana prawns from Chantaburi province were significantly higher (P < 0.05) than those from Trat province. There was no significant difference observed between the contents of Pb, Ni, and Cr in banana prawns caught from the two provinces. Heavy metal content in banana prawn, especially in cephalothorax tissue, may be a good indicator (sentinel organism) of heavy metal contamination in the coastal environment. Mean concentrations of all heavy metals in abdominal muscle (edible part) were within the safety limits for human consumption. However, Cd and Cu concentrations in some of the cephalothorax samples from Chantaburi province were higher than the safety limits for human consumption. This suggests that a close monitoring program is needed to ensure the safety of F. merguiensis as a food source.