This article addresses the issue of project maturity in non-profit organisations, where project activities are the basis of operations and fulfil an important social role. This is a topic that has not yet been sufficiently researched. The presented research area is interesting for the management practices of non-profit organisations, and fits into the stream of research on the effectiveness of project implementation. It responds to the current needs of increasing professionalism in project management in non-profit organisations, which translates into more effective implementation of projects and the satisfaction of beneficiaries. It was noted that project maturity surveys can be an important source of information about non-profit organisations, and that gaining knowledge about project maturity can be seen as the beginning of a process to improve the organisation of project management. The conclusions drawn are based on a survey of a sample of 93 non-profit organisations operating in Poland.