The efficiency of maintenance processes in an enterprise largely depends on ensuring adequate resources for its implementation. The main factor that affects the quality of these processes is competent employees. Their knowledge, skills and ability to respond to unexpected situations largely determine the efficiency of the functioning of the technical infrastructure in an enterprise. In the light of the prospects for the development of the Industry 4.0 concept, and, thus, for the development of highly automated systems, the demand for qualified maintenance employees will increase. Therefore, in order to ensure the right level of competency of maintenance workers, through the proper assessment and identification of their competency gap, is an important task of managers. In many enterprises this is not implemented. The aim of the presented work was to developed a comprehensive model of the competency assessment of maintenance workers. The implementation of the developed model enables the identification of the current level of employees’ competencies and identification of the competency gap, as well as it allows to assess the effects of a failure to meet the required level of competency. Additionally, the results of the identification of the real activities taken by the surveyed enterprises concerning the competency assessment of maintenance services employees are presented in this article. The study was carried out in manufacturing enterprises in different industries on a specific area. The results were analysed and presented in a graphic form.