Objective: The genus Trichoderma comprises a great number of fungal strains that act as biological control agents, the antagonistic properties of which are based on the activation of multiple mechanisms.Methods: Trichoderma strains exert biocontrol against fungal phytopathogens either indirectly, by competing for nutrients and space, modifying the environmental conditions, or promoting plant growth and plant defensive mechanisms and antibiosis, or directly, by mechanisms such as mycoparasitism. In order for identification of Trichoderma species, sampling was performed from plant tissues and soil samples of medicinal plants in the South Khorasan province during 2012-2114 years. Several isolates of Trichoderma were isolated from soil and tissue samples using the Trichoderma selective medium.Results: Isolates were identified based on macroscopic and microscopic morphological characteristics such as a growth and shape of the colony, type of conidiophore formation, shape and size of phialide and conidium on CMD and MEA and using valid Trichoderma keys. So far, four species were identified harzianum, crassum, brevicompactum, and virens spices. T. harzianum was the most frequent species among isolates and isolated from Russian olive, Camelthorns, Jujube, Barberry and Basil samples.