This study of the composition of heavy metal, lead, iron, zinc and mercury in periwinkle tissues (Tympanotonosfiiscatus) were determined from different sampling stations in Mgbuoshimini Port Harcourt, Rivers State, Nigeria, using Atomic Absorption Spectrophotometer (AAS). The results obtained from the analysis of salt water and fresh water periwinkle tissues indicated lead 18.62%, iron 70.08%, mercury 11.20% and zinc 53.34% and that of fresh water periwinkle includes 17.48%, 71.79%, mercury 10.71% and zinc 48.28% by percentage conversion. This comparative analysis implies that the fresh water periwinkle tissues have higher concentrations of iron and zinc which can be attributed to the dissolved mineral resources available in both salt and fresh water bodies. However, the concentrations of lead and mercury in these water bodies are above threshold limit which is quite a potential hazard for sea foods. In conclusion, comparison between the two water bodies showed that tissue samples from fresh water had higher concentration of metals in relation to salt water indicating potentials for accumulation, mainly due to differences in anthropogenic activities. Hg, Zn, Fe and Pb concentrations in tissue had values higher than the recommended limits in seafood by FAO/WHO however, regular monitoring is required to observe perturbations. In addition, sea foods obtained from the salt and fresh water bodies are potential sources of heavy metal poisoning, due to industrialization and non-regulatory use of the water bodies, thus, calls for adequate legislation and proper orientation on the use and protection of water bodies from heavy metalpoisoning.