Portunus pelagicus (crab) shells are considered a delicacy by many throughout Asia. In most instances, the specie is highly prized as the meat is sweet. This study was conducted to investigate the common water-contaminant adsorption capacity of chitin from Portunus pelagicus (crab) shells under different concentrations and compare its adsorption capacity with that of standard adsorbents. Demineralization was done to the shells using a standard HCl solution for 24 hours to remove all existing minerals. The demineralization and deproteination processes were based on the methods of Takiguchi (1991). Demineralized and deproteinized crab-shell was subjected to qualitative tests to confirm the presence of chitin using the methods of Richards and Campbell. The percentage adsorption activities were determined by comparing the concentration of the contaminants before and after chitin were added to the solution. It was observed that adsorption activity increases as concentration of chitin increases. Thus, it is more effective in higher concentrations. The results revealed that chitin from Portunus pelagicus offer adsorption sites for the common water contaminants since it is composed of chitin fibrils, arranged with units of amino groups and oxygen that makes it ideal for adsorbing different materials; hence, it can be an efficient substitute for synthetic adsorbents for common water contaminants for it does not pose any danger to human health.