The Grampositive marine bacterium Jeotgalicoccus halophilus (Firmicutes) was isolated from the octocoral Antillogorgia elisabethae (syn. Pseudopterogorgia elisabethae), and cultivated in LBS medium. An organic extract from the supernatant of this culture showed to be active as quorum sensing inhibitor using Chromobacterium violaceum ATCC 31532 as biosensor. Different growth parameters, including culture volume, shaking speed and time, were evaluated for the QSI compounds production. From the crude extract seven compounds were isolated by chromatographic techniques using a bioguided approach, and its structures were determined by NMR, UV and MS analysis. A new cyclic peptide was identified as cyclo-[Prolyl-Valyl-Prolyl-Phenilalalyl] (1), together with the phenolic compounds 4-(methylthio)-phenol and p-hydroxybezaldehyde (2-3), the indols 3-indolaldehyde and (1-H-indol-3-yl)oxoacetamide (4-5), the 2-methylpropanoamide (6), and the sulphur containing compound thiobenzoic acid (7), which production is increased by addition of agar to the culture media. A strong quorum sensing inhibition (QSI) activity was observed for compounds 1-7 at concentrations of 0.23, 0.36, 1.64, 0.34, 0.27, 0.36, and 4.6 mM, respectively (Kojic acid was used as positive control showing QSI activity from 1,4mM).