Bacterial quorum sensing refers to the ability of bacteria to control gene expression through the detection of a threshold concentration of certain chemicals called autoinducer(s), which are secreted by self and/or other bacteria. Quorum sensing is implicated in the regulation of pathologically relevant events such as biofilm formation, virulence, conjugation, sporulation, and swarming mobility. Inhibitors of bacterial quorum sensing are valuable research tools and potential antimicrobial agents. In this paper, we describe the discovery of several boronic acid inhibitors of bacterial quorum sensing in Vibrio harveyi with IC(50) values in the low to sub-micromolar range in whole cell assays.