Efforts to control bacterial infectious diseases are carried out by giving natural antibacterial. One of the natural antibacterial sources is marine fungi, including algae extracts and mangrove leaves. The study aimed to analyze the antibacterial properties and active compound of endophytic marine fungi Aspergillus terreus extract against Salmonella Typhimurium. The methods used in this study include cultivation, extraction, antibacterial test, fractination using Thin-layer Chromatography (TLC), and bioautography. The data obtained were analyzed descriptively. The result showed that the Aspergillus terreus isolates that were cultivated on the nine days have maximum antibacterial activity around 8.88 mm (level 2 mg), 6.61 mm (level 1 mg), and 4.91 mm (level 0.5 mg). The active compounds contained in the extract of Aspergillus terreus were steroids, phenols, and flavonoids. Fractionation with TLC and bioautography showed an inhibitory zone of Aspergillus terreus was 17.7 mm at retention factor (Rf) values of 0.9, 0.83 (λ=254 nm) or 0.8 (λ=366 nm). In conclusion, Aspergillus terreus as marine fungi from mangrove leaves cultivated for nine days, had the largest inhibition zone diameter 8.88 mm (level 2 mg). The active compounds of fungi were steroids, phenols, and flavonoids.