This paper focuses on the role of evidence-based knowledge in improving civil society engagement in international development policy processes. Section 1 focuses on the role that evidence-based knowledge can be used by CSOs to improve their role in policy processe, and aims to outline why evidence matters for CSOs’ work in international development. Section 2 the scene and highlights the opportunities and challenges facing CSOs policy work. Section 3 provides a framework that matches the engagement mechanisms and evidence needs to the critical stages of policy processes. Section 4 summarises strategic and practical advice regarding how CSOs can ensure their policy engagement is more effective, influential and sustained.