The protective activity of a non-bacteriocinogenic Lactococcus piscium CNCM I-4031 strain against Listeria monocytogenes was investigated in tropical cooked peeled shrimp stored at 8°C in modified atmosphere packaging (50% N2-50% CO2). When inoculated alone (L. piscium 107 CFU g-1 and L. monocytogenes 104 CFU g-1), protective culture and target strain grew very well on shrimp reaching a maximum cell number of 109 CFU g-1 after 7 and 14 days, respectively. In the presence of L. piscium, growth of L. monocytogenes was totally prevented after 3 days of storage. The count was 3.4 log CFU g-1 lower than in the control after 10 days and until the end of storage (31 days). Using the Seafood Spoilage and Safety Predictor Software (http://sssp.dtuaqua.dk), it was shown that pH decrease from 6.58 to 5.94 and lactic acid concentration of 89.65 mM measured in the co-inoculated batch did not fully explain the inhibition observed.