Nile tilapia (Oreochromis niloticus) is one of the most commercialized fish species in Brazil. The generation of residues from fish processing refrigerators can represent about 70% of the total mass of the fish. Knowing the characteristics of these byproducts is fundamental to make better use of them, thus contributing to the reduction of the environmental impact as well as to the increase of the profitability of the industries. Thus, the present study aimed to characterize physical-chemically filleting residues of the nile tilapia. Carcass, mechanically separated meat (CMS) and skin were analyzed for the following aspects: water activity (aw), humidity, pH, lipids and ashes. All analyzes were performed according to the official methodology. The aw of CMS, carcass and skin were 0,994, 0,991 and 0,998, respectively, with no significant difference between these results. The high humidity levels of CMS (45,56%), carcass (68,91%) and skin (69,96%), associated with high levels of aw, confirm the high perishability of these residues. The pH values found for CMS, for carcass and for skin were 7,83, 6,53 and 7,24, respectively. The pH near neutrality demonstrates once again the need for adequate preservation, avoiding the development of microorganisms. The lipid fraction of the carcass (7,53%) was approximately nine times higher than the CMS (0,84%) and almost three times higher than the lipid content of the skin (2,77%). There was a significant difference between the levels of CMS (23.27%), carcass (7,11%) and skin (0,31%). Processing residues of Nile tilapia emit distinct physical-chemical characteristics, which represent an opportunity for the development of new products by adding value to a discarding material.