Construction project success is normally assessed based upon time, cost and quality. One or more of these three key measures of success are often not met and one factor contributing to this is the increasing complexity of modern construction projects. However, little research into the understanding of construction project complexity and its effect on key measures of success has been conducted. Whilst much of the recent research has been focused on evaluating projects using risk assessment and management systems; the assessment of project complexity remains by implication rather than application and understanding. No formal project complexity measurement or evaluation tools currently exist and there is a clear need for this in practice. The aim of the research was therefore to develop a model to evaluate the effects of project complexity on project success at the pre construction stage with a particular reference to increasing the accuracy of predicting project time, cost and quality outcomes