Complexity is a critical factor in managing a project, as it presents an additional difficulty in achieving the project’s objectives. As complexity makes a project more challenging to understand and keep under control, agile methodologies have been developed to enable increased flexibility and responsiveness to changing conditions. Therefore, it is essential to empirically examine the moderating effect of project complexity on the relationship between agile response-to-change (AR) and project performance. To address this objective, a questionnaire was used to measure project complexity, project performance and AR. Structural equation modelling was used to explore the relationship between these variables. The results suggested that internal AR has a positive effect on budget performance. Project complexity appears to lower the relationship between internal AR and schedule performance. As one would expect, the higher the level of project complexity, the more likely the project is to experience delays.