Four major phenolics were demonstrated to be produced by Pseudomonas fluorescens strain CRb-26, a cotton rhizobacterium antagonistic to Xanthomonas camprestris pv. malvacearum (Xcm), the inducer of bacterial blight of cotton. Of these, compounds II (nonfluorescent) and IV(fluorescent) completely inhibited the growth of Xcm in vitro. Among these, compound IV was produced maximally (39% of the four phenolics), and it protected cotton leaves from blight infection better than compound II under glass-house conditions. Compound IV, identified as 2,4-diacetylphloroglucinol, was, therefore, concluded to be a key metabolite involved in disease suppression by strain CRb-26 of P. fluorescens, which could be used as an ecofriendly potential input in the integrated management of bacterial blight of cotton.