Plant growth-promoting bacteria (PGPB) are increasingly used in agriculture to enhance plant growth and reduce reliance on chemical fertilizers and pesticides. This review discusses the mechanisms by which PGPB promote plant growth and their applications in sustainable agriculture. PGPB can enhance plant growth through direct mechanisms such as nitrogen fixation, phosphate solubilization, and iron sequestration, as well as indirect mechanisms like modulating plant hormones and inducing systemic resistance. Nitrogen fixation involves bacteria like Rhizobia and Azospirillum, which convert atmospheric nitrogen into a form usable by plants. Phosphate solubilization helps make insoluble phosphorus available to plants, while iron sequestration involves the production of siderophores that bind iron and facilitate its uptake by plants. PGPB also influence plant hormone levels, such as cytokinins and indoleacetic acid (IAA), which regulate plant growth and development. Ethylene production, a stress hormone, can be reduced by PGPB that produce ACC deaminase, thereby improving plant growth. Additionally, PGPB can act as biocontrol agents by producing antibiotics, lytic enzymes, and siderophores that inhibit plant pathogens. They can also compete with pathogens for nutrients, reducing disease incidence. PGPB can also help plants withstand environmental stresses such as drought, high salinity, and temperature extremes by modulating hormone levels and enhancing stress tolerance. Despite their potential, the commercialization of PGPB faces challenges related to regulatory approval, public perception, and the need for effective application methods. As understanding of PGPB mechanisms improves, genetic engineering may lead to more efficient strains. Overall, PGPB offer a sustainable alternative to chemical inputs in agriculture and have the potential to significantly impact future agricultural practices.Plant growth-promoting bacteria (PGPB) are increasingly used in agriculture to enhance plant growth and reduce reliance on chemical fertilizers and pesticides. This review discusses the mechanisms by which PGPB promote plant growth and their applications in sustainable agriculture. PGPB can enhance plant growth through direct mechanisms such as nitrogen fixation, phosphate solubilization, and iron sequestration, as well as indirect mechanisms like modulating plant hormones and inducing systemic resistance. Nitrogen fixation involves bacteria like Rhizobia and Azospirillum, which convert atmospheric nitrogen into a form usable by plants. Phosphate solubilization helps make insoluble phosphorus available to plants, while iron sequestration involves the production of siderophores that bind iron and facilitate its uptake by plants. PGPB also influence plant hormone levels, such as cytokinins and indoleacetic acid (IAA), which regulate plant growth and development. Ethylene production, a stress hormone, can be reduced by PGPB that produce ACC deaminase, thereby improving plant growth. Additionally, PGPB can act as biocontrol agents by producing antibiotics, lytic enzymes, and siderophores that inhibit plant pathogens. They can also compete with pathogens for nutrients, reducing disease incidence. PGPB can also help plants withstand environmental stresses such as drought, high salinity, and temperature extremes by modulating hormone levels and enhancing stress tolerance. Despite their potential, the commercialization of PGPB faces challenges related to regulatory approval, public perception, and the need for effective application methods. As understanding of PGPB mechanisms improves, genetic engineering may lead to more efficient strains. Overall, PGPB offer a sustainable alternative to chemical inputs in agriculture and have the potential to significantly impact future agricultural practices.