Cold plasma (CP) is a non-thermal technology, successfully used to decontaminate and extend the shelf-life of various foods. However, CP can cause quality deterioration in sensitive matrices, such as fish products. This research aimed to evaluate the effect of CP treatment obtained using different gas mixtures (80% Ar/20% O₂, or 80% N₂/20% O₂) with a surface dielectric barrier discharge (SDBD) on the decontamination of spoilage microflora, the main quality indices and the sensory acceptability of seabream (Spaurus aurata L.) fillets during refrigerated storage. At the beginning and at the end of the shelf life, lipid and protein oxidation indices and the fatty acid profile were evaluated. Results showed that, despite a low initial microbial decontamination (0.2–0.3 Log CFU/g), an inhibition of the growth of the main spoilage bacteria was observed resulting in an increase of the microbiological shelf life of around 40% for both treatments. Although a slight increase in lipid and protein oxidation was observed (up to around 5 mg MDA/kg and 4 nmol/mg of protein for TBARs and carbonyl content respectively), the sensory acceptability was higher for plasma treated samples, while the fatty acid profile was not affected and only a slight variation in the surface colour was observed (L* value increase by 3 points), confirming that CP could represent an interesting strategy to extend the shelf life of seafood products with minimal impact on quality and nutritional value.