Gouramy (Osphronemus gourami Lac.) is a freshwater fish in Indonesia that can be infected by Aeromonas hydrophila, leading to motile Aeromonas septicemia (MAS). This study aimed to evaluate the antibacterial potential of bioactive compounds from the Avicennia marina mangrove plant to control A. hydrophila infections in gouramy. Using a completely randomized design, the researchers tested four concentrations of A. marina leaf extracts (0g L–1, 0.2g L–1, 0.3g L–1, and 0.4g L–1) with four replicates. The leaves were extracted using methanol, and infected fish were soaked in the extracts for 60 minutes, with recovery monitored over 14 days. The study assessed disease symptoms, recovery, and survival rates, analyzing survival data with ANOVA and Duncan's test. Symptoms of MAS included skin depigmentation, ulcers, hemorrhaging, abdominal dropsy, fin erosion, and exophthalmia. Recovery began on days 7-8 for the treated groups, while control fish showed decreased appetite and ongoing symptoms. Statistical analysis revealed that A. marina extract significantly improved survival rates (P<0.05), with the most effective concentration being 0.2g L–1. The findings suggest that A. marina leaves could serve as a natural resource for developing anti-A. hydrophila treatments.