Introduction: The Dutch Solid Start program aims to improve the collaboration between the medical and social sector to offer every child the best start in life. Municipalities form local coalitions of partners within the medical and social sector to support parents and children during the first thousand days. The aim of this study was to develop an indicator set for coalitions to monitor their local Solid Start program. Methods: A modified Delphi study with three rounds was carried out among Dutch experts in Solid Start practice, policy and research (n = 39) to reach consensus. Results: The indicator set included 19 indicators covering the three phases of the Solid Start program: preconception, pregnancy and after birth (up to two years). Prioritized indicators included both social and medical topics, among which poverty, psychological/psychiatric problems, stress, smoking, cumulation of risk factors, preconception care, low literacy, premature birth, and intellectual disability. Additionally, a development agenda was established with topics and indicators that lacked data or clear operationalization (e.g. stress, unintended pregnancy, loneliness). Discussion and conclusion: The developed indicator set enhances the conversation between policymakers, managers, professionals and other stakeholders about the local situation and developments in order to prioritize interventions and policies. Next, the indicator set needs evaluation to assess its usefulness.