This paper examines the problem of measuring the maturity of quality management systems. The main scope of the study is to measure the level of maturity of quality management systems in organizations with an implemented quality management system compliant with the requirements of ISO 9001 in Poland; however, this paper also investigates which factors influence the level of maturity. An analysis of the maturity level of the quality management system in the surveyed organizations showed that the highest level of maturity occurs in those areas and activities that directly result from the requirements of the ISO 9001 standard and direct market pressure, and this level of maturity must be implemented. This can be included in case areas such as customer orientation, process approach, or evidence-based decision-making. However, a lower level of maturity is observed in the case of “soft” aspects of quality management related to leadership and human resource management. The problems are also related to the implementation of corporate social responsibility (CSR). In this respect, the surveyed organizations show numerous shortcomings which lead to low assessments of their level of maturity, for example, in ensuring openness and ethical behavior in contact with the public. The following hypothesis was formulated for the research objective: H1—control variables, such as the size of the organization (H1a), time of existence of the enterprise (H1b), business profile (H1c), market position (H1d), financial condition (H1e), and ratio of management to the normalization processes (H1f), affect the level of maturity of an enterprise’s quality management system.