In the article the question of definition of specificity of mathematical competence as a component of the system of professional competencies of future workers of machine building profile is considered. Based on the study of scientific and pedagogical literature, the analysis of definitions of mathematical competence and components of mathematical competence is carried out. A list of general professional competencies of future workers in the machine building based on the analysis of regulatory legal documents. In the course of the research, the concept of mathematical competence of pupils of vocational school of a machine-building profile was defined. The components of mathematical competence of pupils of vocational school of a machine-building profile are singled out: motivational, cognitive, activity, reflective-valuable and personal and their essence is revealed. As a result of the research, the author presents a connection between the components of mathematical competence and general professional competence of future workers in the machine building profile. The author indicates the place of mathematical competence in the system of professional competencies of future machine building workers. The author makes a conclusion about the advisability of developing the mathematical competence of pupils of vocational school of a machine-building profile.