This research investigates the biochemical profile, antioxidant properties, and antigenotoxic activity of red seaweed (Gracilaria sp.) extract on micronuclei formation in peripheral blood erythrocytes of tilapia (Oreochromis niloticus) exposed to a methomyl-based pesticide. Results revealed a diverse phytochemical profile in the red seaweed extract, with the presence of alkaloids, triterpenoids, steroids, tannins, coumarins, terpenoids, quinine, phytosteroids, flavonoids, and phlobtannins. GC-MS analysis identified compounds such as Heptadecane, Neophytadine, Hexadecanoic acid, Oleic acid, and Adipic acid in the sample. The antioxidant activity exhibited a concentration-dependent response, demonstrating increased strength with higher extract concentrations. Antigenotoxic analysis indicated a significant reduction in micronuclei frequency in peripheral erythrocytes of tilapia. In conclusion, the research underscores the potential of red seaweed extract as a valuable natural resource with antioxidant properties and a mitigating effect on genotoxicity induced by pesticide exposure in aquatic organisms.