The pathogen can spread rapidly from plant to plant during the growing season and high losses in both yield and quality can subsequently occur in vegetable and forage brassicas. Currently, there is no effective control method. Biological control may offer an option for control of this seed borne disease. Potential microbial biocontrol agents were isolated from commercial cabbage and rape seed lots as part of the “Smart Seeds for Export” research programme at the Bio-protection Research Centre and one of the promising microbes was the bacterium Paenibacillus. This research therefore addresses the use of Paenibacillus applied as a seed treatment for biological control of black rot on cabbage. Based on dual culture assays, 24 isolates of Paenibacillus were categorized for their interactions with Xcc. Eight of these isolates with different bioactivity in suppression of Xcc in vitro were then screened for their capacity to reduce black rot symptoms on cabbage in pot trial assays. From these results one Paenibacillus isolate (P16), at the concentration of 5 × 109 CFU/ml was selected as a potential biocontrol agent. To investigate if the disease control was provided via plant growth promotion, the P16 isolate was co-applied with Xcc as a seed treatment. In the presence of Xcc, P16treated seedlings had significantly (P ˂ 0.05) greater growth parameters including root length, leaf area, and root and shoot dry weight compared to the control. However, there was no significant difference in plant growth parameters between P16-treated seedlings and the control in the absence of the pathogen.