The beneficial fungus Trichoderma harzianum spp. works effectively in the protection of phytopathogenic fungi in vegetable production, and according to many scientific studies, it can be successfully used in the protection of phytopathogenic viruses, harmful insects and phytonematodes as an adequate alternative to chemical pesticides. It can also be used as an alternative to mineral fertilizers since it is a natural agent for the decomposition of organic substances, an intermediary source of nutrients and an excellent promoter of plant growth. All over the world, T. harzianum is isolated from the soil, propagated and on its basis or in combination with several antagonistic bio agents, biofungicides, biofertilizers and plant inoculants are produced as plant strengthening agents. Plant inoculants are not classified as biofungicides, but they have the same effect on plant pathogenic microorganisms, harmful insects and phytonematodes. In interaction with pathogenic microorganisms, T. harzianum develops mechanisms of action (parasitism, competition, antibiosis and induced resistance) by which it overcomes and directly suppresses plant pathogens, while in interaction with the plant it establishes a symbiotic relationship and induces and activates the plant's defense system so that the plant indirectly reduces pathogens diseases and pests naturally. Injurious insects, T. harzianum controls by parasitism, production of secondary insecticidal metabolites, compounds that repel insect feeding and production of repellent metabolites, while phytonematodes are controlled directly through competition, paralysis, antibiosis, parasitism, production of lytic enzymes or can indirectly induce systemically acquired resistance of the plant that is can inherit by seed. The use of biopreparations based on T. harzianum has many advantages compared to chemical protection because there is no accumulation of chemical substances in the soil, water, air, there are no residues in plant and animal products and there is no damage to beneficial organisms, animals, humans. They don’t cause phytotoxic damage to plants. Pathogenic microorganisms and pests can’t develop resistance, and can contribute to a significant reduction of greenhouse gas emissions and establish sustainable vegetable production.