This study aims to isolate endophytic fungi from the roots of mangrove from Riau Province’s Mangrove Forest and to screen some isolates with ability to inhibit the growth of pathogenic bacteria. A total of 28 endophytic fungi have been isolated from mangrove samples identified as Bruguiera sp. and Ceriops tagal (Perr.) C.B.Rob. Out of 28 isolates, 17 isolates (60,71%) were isolated from direct plating of sterile segment of root samples, while 11 isolates (39,28%) were isolated from suspension of grinded sterile segment in aliquot sterile sodium chloride. The potency of all isolated endophytic fungi to produce antibacterial agents were identified by doing antagonistic study against Escherichia coli, Staphylococcus aereus and Vibrio alginolyticus. The results showed that the highest antibacterial activity was produced by the isolates of C7B, B1C, C4E, and C4D with clear zones diameter of 17.91 ± 0.84 mm; 17.78 ± 0.83 mm; 17.66 ± 0.83 mm; 16.72 ± 1.15 mm, and 13.65 ± 0.27 mm, respectively. Based on macroscopic and microscopic analysis, those fungal isolates were identified as Penicillium sp. (C7B) and Trichoderma sp. (B1C, C4E, C4D).