The recent and increasing body of evidence indicates a strong relationship between poor WASH and stunting, and stresses the need for joint Nutrition and WASH interventions for improving nutrition outcomes. Responding to growing demand for practical guidance on joint Nutrition – WASH programming and actions, this EAPRO led WASH-Nutrition Toolkit is the first of such resources for use by national and local government authorities, UNICEF staff, NGOs and other stakeholders. The toolkit summarizes the latest evidence base on the rationale and importance of joint programming as well as practical steps on how to strengthen joint WASH and Nutrition programming and actions, including a process for developing a joint Theory of Change.