Aims: To study the potential biocontrol activity of bioflocs technology. Methods and Results: Glycerol-grown bioflocs were investigated for their antimicrobial and antipathogenic properties against the opportunistic pathogen Vibrio harveyi. The bioflocs did not produce growth-inhibitory substances. However, bioflocs and biofloc supernatants decreased quorum sensing-regulated bioluminescence of V. harveyi. This suggested that the bioflocs had biocontrol activity against this pathogen because quorum sensing regulates virulence of vibrios towards different hosts. Interestingly, the addition of live bioflocs significantly increased the survival of gnotobiotic brine shrimp (Artemia franciscana) larvae challenged to V. harveyi. Conclusions: Bioflocs grown on glycerol as carbon source inhibit quorum sensing-regulated bioluminescence in V. harveyi and protect brine shrimp larvae from vibriosis. Significance and Impact of the Study: The results presented in this study indicate that in addition to water quality control and in situ feed production, bioflocs technology could help in controlling bacterial infections within the aquaculture pond.