Project governance can potentially provide the top management support needed for projects to succeed. However, the awareness and adoption of project governance guidelines has been sporadic. This research seeks to overcome any credibility gaps that may exist by developing a theoretical model to explain why project governance should work and testing the model against industry data. The research found five of six theoretical constructs for project governance correlated significantly with project success and different constructs were more important at different at different stages in the project lifecycle. The contribution of the research is firstly to show project governance can be explained by agency theory and theories of planned change. The second major contribution is to provide evidence that project governance leads to project success.