Bacterial panicle blight (BPB) of rice, caused by Burkholderia glumae, affects rice production worldwide. Currently, there are no rice varieties that are completely resistant to the disease, and chemical control methods are not available or effective. Thus, in the absence of completely resistant cultivars or chemical methods of control, an alternative strategy is to identify sources of biological control. The objectives of this study are: 1) to identify bacterial strains that could be used as biological control agents against B. glumae and 2) to dissect their mechanism of control. Ten laboratory strains were initially screened using a disc diffusion assay, and two of them (Pseudomonas fluorescens and Burkholderia cenocepacia) significantly inhibited the growth of B. glumae in vitro. Moreover, co-inoculation of P. fluorescens and B. cenocepacia with B. glumae also reduced disease symptoms in rice. To dissect the mechanism behind the growth inhibition of B. glumae by P. fluorescens and B. cenocepacia, cell-free secreted fractions from P. fluorescens and B. cenocepacia were obtained and used to evaluate the growth of B. glumae. Cell-free secreted fractions in amended culture media reduced the growth of B. glumae in vitro in comparison with non-amended controls. Moreover, when these cell-free secreted fractions were mixed with B. glumae, they hindered the ability of this bacteria to cause disease in rice. These results suggest that these strains of P. fluorescens and B. cenocepacia are promising agents to control BPB.