The current study aimed to screen, identify and evaluate the biological activity of fungi strains from the mangrove plant Acanthus ilicifolius L, which has proven to be a rich source of fungal species. Thirteen fungi were screened from the leaves, stem bark, and roots. Each fungal strain was cultivated in rice as media, and then the secondary metabolites of the fungus were extracted with ethyl acetate. The extracts were tested for antimicrobial and cytotoxic activities. Next, a phylogenetic tree was reconstructed based on the sequence similarities of each strain. The fungal extract AIA1 displayed excellent antimicrobial activity in a concentration of 5 % against some pathogenic bacterial strains with an inhibition zone in the range of 11.87 ± 0.87 to 15.42 ± 0.51 mm. The brine shrimp lethality test (BSLT) showed that strains AIA1 and AIKB3 were toxic against Artemisia salina L with an LC50 value of less than 80 ppm. The MTT assay determined the cytotoxicity against the human ductal breast epithelial tumor (T47D) cell line. Based on molecular identification, AIA1, AIKB3, and AID1 showed maximum similarity (> 95 %) with Pestalotiopsis sp. AIA1, Trichoderma yunnanense AIKB3, and Schizopyllum commune AID1, respectively. The ethyl acetate extracts of fungi strains from the mangrove plant A. ilicifolius showed strong antibacterial and moderate cytotoxic activities, which make them good candidates for secondary metabolite isolation. HIGHLIGHTS This is the first report on exploring the endophytic fungi from the mangrove plant Acanthus ilicifolius collected from Mangrove Forest Tourism Park, West Sumatera, Indonesia Endophytic fungi strains from mangrove plant Acanthus ilicifolius showed good activity on the antimicrobial and cytotoxic assay Three potential endophytic fungi were identified asPestalotiopsis AIA1, Trichoderma yunnanense AIKB3, and Schizopyllum commune AID1 GRAPHICAL ABSTRACT