The current study aimed to explore the effects of mild processing for shelf-life extension on the raw an-d cooked quality of gilthead seabream fillets stored at 2 °C. Control and Treated (via osmotic dehydration) fillets were sampled at the beginning (D1), middle (D5) and end (D7) of commercial shelf life. The raw quality was evaluated via the quality index method (QIM), microbial measurements and for D1 through tetrad discrimination testing. The cooked quality was evaluated for the same samples via sensory descriptive analyses with a trained panel. The tetrad results indicated similar characteristics between treatments for raw fillets on D1 and a 29% shelf-life extension for Treated fillets vs. the Control ones, defined by Quality Index Method and microbial measurements. The raw quality was reflected in the cooked quality of the tissue, with the Treated fillets exhibiting less intense spoilage-related sensory attributes as well as enhanced or retained freshness-related attributes throughout storage, when compared to the Control ones. A range of treatment induced sensory characteristics, partly associated to Maillard reactions, were developed in the Treated fillets. Overall, the treatment affected positively both the raw and cooked quality of the fillet, showing promising results as a shelf-life extension method for fish fillet preservation.