This paper investigates the use of improvisation within the project-managed implementation of strategic change in the UK financial services sector. It contains a brief review of the literature relating to the concepts surrounding organisational improvisation, and considers the emerging literature, organizing it in terms of how it relates to project-based management. Attention is then given to possible future directions for research into project-based improvisation. The data that underpins this study is drawn from a qualitative study of six organizations, chosen for their organizational diversity. The common denominator is that they have all undergone significant strategic change, and have all used project management techniques of varying levels of maturity and sophistication to achieve that change. The main finding of this study is that, notwithstanding the dominant project management paradigm of 'plan, then implement', improvisational working practices are embraced enthusiastically, and used extensively, by almost all interview respondents, who spanned a wide range of project-based roles within the organizations. It is also evident that considerable support for such practices exists at the strategic level and that although there are varying levels of commitment, time and opportunity is provided for employees to improvise to develop emerging best practice. Capturing such practice formally is however less formalized, and it often resides only tacitly in employees, especially in the larger organizations who are managing change on many fronts simultaneously.