The antibacterial activity, phenolic profile, and bioactive compounds of fruiting bodies from 2 strains (MA1 and MA2) of the giant mushroom Macrocybe gigantea were evaluated to access their nutraceutical efficacy. The antibacterial activity was higher in MA2 against all selected pathogenic bacteria. Selected phenolics were analyzed by high-performance liquid chromatography coupled with ultraviolet-visible detection. Gallic acid, ferulic acid, quercetin, p-hydroxy benzoic acid, cinnamic acid, and rutin contents (micrograms per gram dry weight) were quantified. Quercetin and rutin were absent in both strains of M. gigantea. M. gigantea MA2 showed relatively higher phenolic content (915.8 μg/g dry weight) than M. gigantea MA1 (854.4 μg/g dry weight). Among the phenolics, gallic acid is found in the largest amount; in M. gigantea MA2, it was 847.9 ± 2.67 μg/g dry weight. Gas chromatography-mass spectrometry analysis showed the presence of bioactive compounds in both strains; most compounds were antibacterial. Thus, the selected strains of M. gigantea can combat oxidative damage and can be used in foods, pharmaceuticals, and cosmetics because of their antioxidant potential.