Thirty-two marine bacterial strains were isolated from marine samples (seawater and sediments) collected from the Mediterranean Sea, Egypt. They were evaluated for their antimicrobial activity against the fish pathogen Vibrio alginolyticus MK170250, using the agar well-cut diffusion technique. The marine bacterial isolates EM11 showed significant activity against V. alginolyticus MK170250 with an inhibition zone of (10 mm). The isolate EM11 was phenotypically characterized and molecularly identified through 16S rRNA gene sequence analysis as Acinetobacter indicus. Placket-Burman and Box-Behnken experimental designs were applied to optimize the fermentation conditions and increase the bioactive compounds' productivity. The optimized medium was formulated as follows: (gl^-1) Peptone 7 g; beef extract: 2 g; inoculum's size (ml) 0.5; sea water concentration: 75%; pH: 6.02; temperature (°C) 40 for 24h incubation period. A verification experiment was applied to evaluate the basal versus the optimized medium. The optimized growth condition successfully increased the inhibition zone about 3.65-fold with an inhibition zone of 36.5 mm in diameter. To the best of our knowledge, this is the first report of Acinetobacter indicus species from marine sediments and its anti-fish pathogen activity.