In this work organic products were isolated and identified from a marine Bacillus sp. which presented growth inhibition of the pandemic strain of V.
. The inhibitory products were extracted and characterized by spectroscopic and
techniques. Purification of the active products revealed five different diketopiperazines, which were compared with standards from high-performance liquid chromatography (HPLC). Although the diketopiperazines is not a finding of a new metabolite, the interested point or novelity of this work is the ability of diketopiperazines to inhibit the growth of pandemic strain of V. parahaemolyticus. We suggest the possibility of using this compound to reduce the growth and control the proliferation of pathogenic clones of V.parahaemolyticus that cause several problems in aquaculture industry.