The aim of this study was to screen for antimicrobial activity of endophytic fungi isolated from surface-sterilized leaves, small branches and roots of Garcinia monstana (mangosteen) cultivated in Ben Tre province, the Mekong Delta, Vietnam. A total of 101 fungal isolates were isolated from leaves (40 isolates), roots (28 isolates) and small branches (33 isolates) but there were 62 isolates (61.38%) displayed antimicrobial activity at least 1 pathogen. From 62 isolates, 28 isolates were chosen to test the ability against the pathogens by well diffusion method and 11/28 were chosen to identify based on nucleotide sequence from internal transcribed spacer (ITS) rDNA. The sequences from selected fungal isolates showed high degrees of similarity to those of the GenBank reference strains (99% - 100%), all of them were identified as various species of two sub-phylum Ascomycota (9 genera) and Deuteuromycota (2 genera). There were three fungal strains (CL18L, CL05R and CL02C) had high ability of antimicrobial activity with 7 pathogens (composed of 2 strains of Bacillus cereus, 2 strains of Escherichia coli, 2 strains of Salmonella and 1 strain Candida albicans. To the best of our knowledge, our results are the first report about diversity of fungal endophytes together with their metabolites in Garcinia monstana plant cultivated on alluvial soil in the Mekong Delta, Vietnam.