Today’s fast-changing market environment makes certain demands on the management system of modern companies. The management system, represented by the enterprise architecture, should have a balanced structure and be mature enough to promptly react to inner and outer business challenges. The system approach to enterprise management means that enterprise architecture components must be formed, reformed and developed taking into account their interdependency. As processes and projects are core components of business architecture, not only they seriously influence, but also define its maturity level. There are a number of existing process and project management maturity models, but no well-known research concerning their joint maturity and the maturity of business architecture. The balance between maturity levels of the mentioned components as a key factor of the balanced business architecture and its development is in the focus of the paper. Analysis of the existing processes and project maturity models has shown that there is a high correlation between maturity levels of these management approaches. Combination of process and project management maturity levels is a reliable diagnostic tool for estimating whether the business architecture is balanced or not. At the same time combination of the maturity levels of process and project management in the company is a way to determine the path of sustainable development of the company’s management system. The paper is focused on exploring the ways to manage business architecture maturity via its key components’ maturity management.