Control as a primary project governance mechanism and a basic managerial function has been extensively utilized in projects which embrace principal-Agent relationships. Prior studies have shown that control is an effective strategy in mainstream principalagent relationships for principals to motivate their agents to behave in a desired manner and deliver satisfactory outputs. However, little is known about how principals perform control when agents are professionals providing intangible services in professional service projects. Therefore, this study aims to address the research question of how clients determine control strategies (including control modes and intensity) in design consulting projects. The specific research objective is to develop a conceptual framework for determining control modes and intensity in design consulting projects. Based on literature review and agency theory, this conceptual paper establishes a framework comprising antecedents of control modes and control intensity which indicate the feasibility and necessity of control respectively. This study enriches the knowledge about how to determine control strategies in professional service projects. Also, it expands the application of agency theory by delineating a particular type of principal-Agent relationship of which agents are professionals.