Plant diseases are caused mainly by fungi, bacteria, viruses, and nematodes, and their control is necessary to feed an increasing population. Control of plant diseases often rely on chemical pesticides, which have contributed to improvements in crop productivity and quality over the past years. However, the intensive use of agrochemical pesticides results in soil and groundwater pollution. Consequently, there are worldwide efforts to develop other alternatives to chemical pesticides for controlling plant diseases. Among them, the use of microorganisms and their products, referred as biological control, are regarded as promissory alternatives to reduce the use of chemical products. Different Bacillus species excrete peptides and lipopeptides to the culture medium, such as fungicine, iturin, bacillomicine and others, that have antifungal antibacterial and surfactant activity. In addition, these species produce spores that are resistant to heat and desiccation, which allows the preparation of more stable and durable formulations. A variety of biological control products based on Bacillus species are available for agronomical use; but in order to translate these developments into a broader and more effective use, a greater understanding of the complex interactions among plants, microorganisms, and the environment is required. This chapter describes some mechanisms of biocontrol exhibited by species of Bacillus, the current status of research and application of biological control using Bacillus species, constraints to microbial biocontrol implementation, and briefly outlines the future directions that might lead to the development of more diverse and effective biological controls for plant diseases.