This study investigates the tissue-specific accumulation and detoxification of nickel (Ni) in Pomacea insularum, a freshwater snail, collected from 13 sites in Peninsular Malaysia. Ni concentrations ranged from 3.24 to 33.38 mg/kg dry weight across eight tissues, including the shell, cephalic tentacle, mantle, digestive tract (DT), foot, remaining soft tissues, pineal sac, and operculum. The shell exhibited the highest Ni accumulation (22.12-33.38 mg/kg), serving as the primary long-term repository, while soft tissues such as the DT (5.55-27.44 mg/kg), mantle (5.44-16.60 mg/kg), and foot (4.49-10.14 mg/kg) played critical roles in initial Ni uptake and redistribution. A field transplantation study further confirmed these findings, demonstrating significant Ni accumulation in soft tissues within seven weeks of exposure to a polluted site, followed by substantial depuration upon transfer to a cleaner environment. Correlation and factor analyses revealed strong interactions between soft tissues and the shell, indicating a coordinated Ni detoxification and storage system. These results underscore the suitability of P. insularum as an effective biomonitor for assessing both short-term and long-term Ni pollution in freshwater ecosystems.