During the most recent global crisis due to COVID-19 pandemic, mental health researchers globally were tasked with carrying out high-quality and responsive research to understand the changes and long-term trajectories in young people’s mental health symptoms. Comparative international longitudinal research has been recommended as a particularly promising avenue to understand pandemic impacts and facilitate global solutions. The Co-SPACE International Consortium comprises researchers from 14 sites who aimed to compare findings on the impact of the pandemic on young people and family mental health. This paper describes the process and challenges associated with the Consortium’s efforts to combine country-level data to produce global insights for research and clinical practice for the past three years. Several key challenges were identified, particularly about the conduct of international comparative research. These challenges concerned funding, ethics review, data sharing, variations in cultural and local contexts, lack of cross-culturally comparable or meaningful measures, research design, and dissemination. After considering these challenges, we provide a range of recommendations that provide a blueprint for the gathering of timely and robust evidence, the identification of global trends, the mobilisation of resources, and effective support to children and families in public health crises.