Abstract: Background and Objective: Shrimp shell waste and crab shell waste are causes of environmental pollution and chemical methods can be used to process this waste into chitosan. Chitosan is the second largest natural biopolymer after cellulose and has many applications in food and health products. The aim of this research was to investigate the potential of Tambak Lorok shrimp shell and crab shell waste as an alternative raw material for chitosan production. Materials and Methods: Chitosan was prepared by chemically treating shell waste from shrimp in the Penaeidae rafinesque family and shell waste from crab in the Portunidae family from Tambak Lorok, Indonesia. The chemical structure of chitosan was confirmed by infrared spectroscopy, oswald viscometry and scanning electron microscopy. Results: The isolated chitosan from shrimp shell waste showed an 89.6% degree of deacetylation, a 64% degree of crystallinity and a 557 kDa molecular weight. The isolated chitosan from crab shell waste showed an 82.1% degree of deacetylation, an 81% degree of crystallinity and a 690 kDa molecular weight. Chitosan from both shrimp shell waste and crab shell waste had a porous and fibril-like structure. Conclusion: It was concluded that shrimp shell waste and crab shell waste are potential alternative raw materials for chitosan production.