My aim is to address the issue of complexity in project management by investigating improvisational practices in projects and project-based organisations. Improvisation is a naturally occurring part of our daily actions. Improvisation is not a practice without structure, it is much rather a form of doing that uses existing processes, experiences and other forms of knowledge to make things work if existing structures fail to produce the projected outcomes. It is often what practitioners do when they face unexpected challenges in their project work. At the same time, I re-emphasise the importance of existing structure, such as processes and capabilities. They are potential starting points for improvisational practices and organisational change. Existing organisational structures therefore become valid tools of practice that should be seen as enablers of actions, rather than constraint jackets, to deliver successful projects.