The screening of antimicrobial compounds from mangrove-associated fungi is a promising way to meet the increasing threat of drug-resistant strains of human pathogens. In the present study, a novel foliar fungus was isolated from the leaves of Rhizophora mucronata. Crude fungal extracts were obtained through solvent extraction. The fungal extracts exhibited an effective antimicrobial activity against bacterial strains. This study reports the cytotoxic activity of the secondary metabolite produced by the fungus against Hep 2 (HeLa derivative) cell line by 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide (MTT) assay. GC-MS investigation of the secondary metabolites revealed the active components of the fungal metabolite. The DNA of the fungus was sequenced by amplifying the ITS region of the 5.8s rRNA to be submitted in the Genbank and an accession number was assigned confirming it to be a new strain.