Fish has great nutritional importance, though highly perishable. The use of biodegradable packaging could be a good strategy in the conservation of environmentally correct frozen fish. The objectives of the present work are as follows: (a) to evaluate the stability of the biodegradable packaging during frozen storage (−18°C) of Pacu fish fillets for 360 days, and (b) to compare the quality of Pacu fish fillets frozen in biodegradable/low‐density polyethylene packaging (LDPE), for 360 days. Biodegradable films with fish stored frozen for a period of 360 days showed stability in chemical and mechanical structure. No band was found in 850–1,000 cm−1 highlighting the inert behavior of the biodegradable packaging. The final tensile strength recorded was 5.93 MPa and elongation at break was 1.02%.The type of packaging had no effect recorded on the quality of the fillets (p ≥ .05). Variable storage time showed an effect on fish quality (p ≤ .05). Practical applications Due to a growing demand for biodegradable packaging in food, the study of the durability of these packages under freezing temperatures becomes important, thus generating information for their diversification and application. The results from this study bring freezing conservation as a new possible use of biodegradable packaging with long shelf‐life, stability in chemical and mechanical structure, without compromising the quality of the preserved fish.