This research focusses on the rancidity stability of mackerel species during frozen storage. Its basic objective was to investigate the effect of including an ethanolic and aqueous extract of algae Bifurcaria bifurcata and Fucus spiralis in the glazing system previously to the frozen storage. For it, two independent experiments were carried out, i.e., employment of a B. bifurcata-glazing system on Atlantic Chub mackerel (Scomber colias) and a F. spiralis-glazing system on Atlantic mackerel (Scomber scombrus). In both cases, quality changes were monitored for a 8-month frozen storage by raw (eyes, external odour, gills and flesh odour) and cooked (flesh odour and taste) sensory descriptors; complementary chemical analyses related to lipid oxidation were also carried out. As a result, both experiments showed a sensory acceptance increase in frozen fish by including algae extracts in the glazing media. This effect showed to be significant (p < 0.05) for descriptors such as eyes, external odour and cooked flesh odour (B. bifurcata experiment), and for external odour, gills and raw flesh odour (F. spiralis experiment). In most cases, an increasing effect could be observed by increasing the content of the alga extract in the glazing system. A novel alga-extract based glazing system is proposed to be applied for the quality enhancement of fatty fish species during their commercialisation under frozen conditions. Such tool can be considered a profitable and practical strategy in agreement with the availability and commercial cost of the materials employed. Further research would be necessary to optimise the experimental conditions.