The study aims at substantiating the entropy approach to assessing the quality of project management processes and developing an appropriate mathematical model. Within the framework of this article, entropy is considered an integral indicator for assessing the project management of Industry 4.0 enterprises, characterizing project controllability and confidence in its results. The quality of project management processes is understood as the ability to assess and minimize, through preventive or adaptive measures, uncertain or negative impacts from the inside and outside, i.e., to ensure a project's success. The authors determine the main factors influencing project entropy. It is substantiated that management is to counteract entropy and create such conditions for project implementation, under which its level is acceptable. A scale for assessing a project's entropy level is proposed, based on experiments. The obtained results allow the authors to assess the quality of management processes at each stage of the project life cycle and to form a theoretical basis for the further development of tools ensuring and improving quality.