Microbiological bioproducts constitute a rapidly growing group of preparations used in modern agriculture and play a significant role in achieving the goals of sustainable crop production. Because they contain live microorganisms or their metabolites, they promote plant growth and development, increase nutrient availability, improve soil properties, and suppress pathogen development, thereby representing a promising alternative to conventional fertilizers and chemical plant protection products. The aim of this study was to analyze the current state of knowledge on the application of microorganisms in agriculture, with a particular focus on their mechanisms of action, bioproduct formulation principles, and the legal requirements for their registration and marketing in Poland and the European Union. The paper presents a classification of microbiological bioproducts and compares their properties with those of chemical products. The stages of product formulation, including strain selection and identification, mass production, the choice of appropriate carriers, and stabilization methods, are discussed. Furthermore, the primary mechanisms of microbial action on plants are characterized, including biological nitrogen fixation, phosphate solubilization, the production of phytohormones and siderophores, and pathogen biocontrol mechanisms. In addition, the current legal regulations governing the classification, registration, and quality and safety requirements of agricultural microbiological products are outlined. The analysis indicates that microbiological bioproducts have significant potential to support sustainable crop production and mitigate the negative environmental impacts of agriculture. However, their widespread adoption requires further advancements in formulation technologies, quality standardization, and the improvement and harmonization of existing legal framework.