The study of Comorian red alga Halymenia durvillei showed a significant biochemical composition with high ash and polysaccharide content and the presence of n-3 and n-6 essential fatty acid molecules. Seasonal monitoring showed a real change in biochemical composition depending on the harvesting period. On an annual average basis, the algae contained 35.59 ± 2.55% dw ashes, 0.7 ± 0.19% dw soluble proteins, 0.27 ± 0.02% dw total lipids, and 35.09 ± 6.14% dw polysaccharides. The pigment composition was 130 µg/g dw R-phycoerythrin, 1.49 µg/g dw chlorophyll a, and 0.09 µg/g dw carotenoids. The most abundant fatty acid identified was palmitic acid (C16:0), which accounted for almost 43.33% of total fatty acids. Oleic acid (C18:1n-9) was the most abundant unsaturated fatty acid, at 11.58%. Linoleic acid (C18:2n-6) was reported to be the most abundant polyunsaturated fatty acid in Halymenia durvillei. The fatty acid profile was also characterized by arachidonic acid (C20:4n-6) and eicosapentaenoic acid (C20:5n-3).