Current issues associated with drug resistance and the adverse effects of synthetic agents have prompted researchers to focus on natural, medicinal agents such as mangroves and their associated fungal endophytes. The current study was developed to determine the antibacterial activities of crude extracts of endophytic fungi isolated from leaves, roots and stems of Acrostichum aureum, Karan koku in Sinhala and Sonneratia alba, Kirala in Sinhala. The endophytic fungal isolates were identified as Aspergillus niger, Aspergillus ochraceus, Aspergillus fumigatus, Aspergillus terreus, Penicillium citrium and Penicillium resticulosum and the respective crude extracts were generated using ethyl acetate. The crude extracts were subjected to antibiotic sensitivity tests (ABSTs) against two test organisms: Staphylococcus aureus (ATCC ®: 25923) and Escherichia coli (ATCC ®: 25922). The highest inhibitory action was exerted by Penicillium resticulosum against both the test organisms (E. coli: 15+0.05 mm; S. aureus 22+0.05 mm) which was the most abundantly identified endophyte in this study. The Minimum Inhibitory Concentration of the crude extracts was detected to be 1. 25 mg/ ml. However, the highest bactericidal action was noted from Penicillium citrinum. It is evident that the fungal endophytes isolated from mangrove plants possess antibacterial properties that can be used as a natural source for the generation of antimicrobial therapeutics.