Fish processing waste, especially collagen-rich connective tissues like skin, scales and bones are an underutilized resource that could contribute to environmental pollution when inappropriately discarded. Still, the non-biodegradability of most petroleum-based plastics creates a need for biodegradable and sustainable packaging alternatives. The goal of this study was to explore Catla catla (Indian carp) processing waste for gelatin extraction and its utilization in developing biodegradable plastic films based on the extracted gelatins. The extraction of gelatin from Catla catla fish waste was performed by a sequential alkaline and acid pretreatment with sodium hydroxide and hydrochloric acid, respectively, followed by sub-lethal thermal extraction at 50–60 °C for 3 h. The resulting extracted gelatin was combined with glycerol as plasticizer to produce thin films via casting method. Biodegradation behaviour of the developed films was assessed under various storage conditions. The resulted gelatin was film-forming and could be manufactured into biodegradable films. Films that were exposed to the environmental conditions gradually degraded, while films stored under closed conditions showed minor alterations and underscored the impact of moisture availability/microorganism activity on polymer degradation. This study showed that processing waste generated during the skin preparation of Catla catla can be a valuable source for gelatin production and utilisation to prepare novel sustainable biodegradable films. Converting fish processing waste into value-added biopolymeric materials opens new avenues for disposal, resource recovery and the sustainable development of eco-friendly alternatives to traditional synthetic plastics.