Vegetables are undoubtedly of prime importance in the world’s diet given their widespread cultivation, diversity of products, and sources of nutrients. This chapter discusses the importance of microbial biostimulants in vegetable cultivation and quality improvement. These microorganisms have demonstrated potentiel effects on vegetable production and crop yield, crop quality and plant protection. On the other hand, we explained various indirect pathogen biocontrol mechanisms (competition for nutrients and niche exclusion, antibiosis by antibiotic-substance production, organic acids and lytic enzymes, stimulation of host tolerance and parasitism or predation) and direct growth promotion mechanisms (fixation of nitrogen, solubilization of phosphate, phytohormone, and siderophore secretion) involved in biofertilization and biocontrol of vegetable crop diseases. Finally, perspectives and challenges in this field of research are illustrated. This review provides the reader and the scientific community with a tool for comprehending the function of microbial biostimulants in vegetable crop production and quality improvement.