Purpose. It is necessary to study of the effect of heterophase inclusions on the technological ductility of steels for various purposes. The goal of the work was to study of the nature and level of plasticity of multiphase inclusions in steels under conditions of hot and cold deformation. Methods. Comprehensive methods for the study of heterophase non-metallic inclusions (metallographic, petrographic, X-ray microanalysis methods) were used. Results. Plastic phases in multiphase inclusions of different types under conditions of hot and cold deformation of steels were investigated. It is shown that each type of multiphase inclusions, which are microcomposite formations in steels, is characterized by its laws of development of deformation processes, which are determined by their chemical and phase composition, structure, deformation ability of the phases of inclusions. Scientific novelty. Peculiarities of plastic behavior of multiphase inclusions of different types are established. The inhibitory effect of non-deformable phases of inclusions on the deformability of plastic phases in a wide range of steel deformation temperatures is established. Peculiarities of the nature of plasticity of multiphase inclusions having different compositions and structure are discussed. Practical significance. Using the results obtained will allow developing technologies for producing steels with regulated content and types of multiphase non-metallic inclusions, which will significantly increase their technological plasticity, as well as prevent the formation of various kinds of defects during the processing of steels by pressure.