This report looks at the role that civil society organisations can play in budget advocacy to address child marriage. It presents the key lessons from six pilot projects designed and implemented by Girls Not Brides member organisations in Kenya, Mexico, Nigeria, Pakistan and Togo at the end of 2019. It also provides key insights into how to conduct budget advocacy to hold governments accountable for budget allocation, and ensure that national policies and programmes addressing child marriage are effectively implemented across sectors and at different levels.