Marine algae, which are the primary producers living in aquatic areas, are the subject of many studies due to their importance as they are eukaryotic and eutrophic organisms that play a crucial role in the pharmaceutical, cosmetic, food, fuel, and textile industries. Macroalgae are known in producing several macronutrients, micronutrients, and other important biologically active compounds (e.g. polyphenols, enzymes, and antibiotics) with potential pharmacological uses. In this research, we aimed to investigate the chemical composition, antimicrobial and antioxidant activities (with three assays), total phenolic (TPC) and flavonoid (TFC) contents of the methanol, ethanol, acetone, and water extracts of Codium fragile (Suringar) Hariot. The LC-ESI-MS/MS assessment allowed the identification of seven compounds containing gallic acid, 4-hydroxybenzaldehyde, 4-hidroxybenzoic acid, p-coumaric acid, salicylic acid, biochanin A, and diosgenin. TPC and TFC of the extracts were calculated as in the range of 10.34±0.13-64.67±0.02 µg GAEs/mg extract and 12.73±2.68-36.78±1.08 µg QEs/mg extract, respectively. All extracts of C. fragile showed antimicrobial activity against all test pathogens at different levels. The methanol, ethanol, and acetone extracts showed different levels of activity against gram-negative and gram-positive bacteria (MIC: 3.125-1.562 mg/mL). The water extract showed the highest activity in ABTS•+ (70.43±14.85%) and DPPH• (72.61±11.44%) assays while the acetone extract exhibited the best activity in CUPRAC (absorbance: 0.60±0.15) assay. The results we obtained approved that C. fragile could be valued as a natural source of bioactive agents for food preservatives and in other industrial and pharmaceutical fields.