Plants are prone to various diseases that significantly impact growth, development, and reproduction. In agricultural production systems, various chemicals are used to control crop diseases, which leads to wider ecological implications such as environmental pollution, development of pathogen strains resistant to agrochemicals, trace chemical residues on produce, and human health problems. To overcome these consequences, the biological control of plant diseases using antagonistic bacteria specifically originating from the phyllosphere is an eco-friendly alternative to chemicals and a supplementary approach for integrated disease management. Interestingly, phyllosphere-inhabiting beneficial bacteria adapted to changing environmental conditions exhibit good biocontrol activity against various phytopathogens in agricultural and horticultural crops. Moreover, phyllosphere bacteria prime plant defenses against various plant diseases through salicylic and jasmonic acid-facilitated immunity pathways. Phyllosphere bacteria also play a significant role in enhancing crop growth and yield through various plant growth-promoting mechanisms. However, the effects of phyllosphere bacteria on crop growth and health are dependent on various biotic and abiotic factors. This chapter provides deep insight into the significance of phyllosphere-associated bacteria as biocontrol agents and their biocontrol mechanisms against phytopathogens. Hence, phyllosphere-associated bacteria may be a prominent source of biocontrol agents for sustainable agriculture and disease management.