Aim: Sea weeds are vital part of complementary and unconventional medicine suitable for the ability to generate secondary metabolites that are used to re-establish health and to treat many diseases. The present study aims at determinining the antioxidant and antifungal activities of the green seaweed Chaetomorpha linum. Methodology: Chaetomorpha linum, collected from the Gulf of Mannar, regions of Mandapam coastal area, Southeast coast of India were reported foremost for the antioxidant and antifungal activities based on the free radical-scavenging activity of the 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH), ferrous reducing antioxidant property (FRAP), and total phenolic content in the methanolic extract. The antifungal properties of the methanolic extract of C. linum were tested against pathogenic fungal strains like Fusarium dimerum and Trichoderma ressei. Results: The DPPH scavenging activity was equivalent to an IC50 value of 8.8 __ampersandsignmu;g/mL ascorbic acid. The total phenolic content was 668.2 mg/g gallic acid equivalent, and the IC 50 value by FRAP assay was 8.6 __ampersandsignmu;g/mL. On further examination, when compared with standard antibiotics, C. linum extract be a sign of considerable activity against Fusarium dimerum and Trichoderma ressei. Conclusion: Our findings represents C. linum is a natural antioxidant and a potential natural source of antifungal agents against selected fungal pathogens.