In Bangladesh, Fusarium proliferatum is a prevalent pathogen of maize plants that poses a significant threat to human health and livestock by producing carcinogenic fumonisin. However, the use of the Bacillus species, which can colonize the infected plant parts, has been practiced globally to mitigate fumonisin contamination in maize. In this study, B. subtilis MMM1, a native isolate from the maize rhizosphere, was found to be the most effective antagonist against F. proliferatum, which reduced their mycelial growth and total fumonisin accumulation by 85.31% and 85.12%, respectively, over control through a fivefold reduction in fungal population (1.1 × 104 CFU/g maize grain) in vitro. Furthermore, out of the five bacilli used in this study, B. subtilis MMM1 was able to increase the root and, shoot length, and the vigor index of maize seedlings, by colonizing the fresh roots at 82 × 106 CFU/g root tissue. This suggests that B. subtilis MMM1 might be put forth both as a biocontrol agent and a plant growth promoter in Bangladesh to combat F. proliferatum. Nevertheless, evaluation of its efficacy in reducing fumonisin contamination in maize should be investigated under field conditions.