This document outlines the scientific strategy and synergy-enhancing activities within the Planetary Health Cluster. The Cluster started its activities on January 1, 2024. The Cluster was kicked off at the meeting in Brussels in June 2024, under the auspices of the final conference of the Horizon 2020 project GoGreen Routes, in Brussels. The Cluster consists of the five projects funded under the Horizon Europe topic HORIZON-HLTH-2023-ENVHLTH- 02-01: GoGreenNext, MOSAIC, PLANET4HEALTH, SPRINGS, and TULIP. These projects aim to improve the identification, monitoring, and quantification of the direct and indirect impacts of environmental changes and degradation on Planetary Health. The Planetary Health Cluster was established by the European Commission to enable the five projects to: ● Harmonize approaches across projects; ● Promote synergies and networking among consortiums; ● Avoid overlaps and redundancies in research and activities; ● Strengthen the Science4Policy link to inform decision-making; ● Streamline information flows between projects and stakeholders; ● Improve communication and dissemination of results; and ● Increase the overall impact of the research. The Cluster’s overarching objective is to clarify the costs and benefits of action and inaction in mitigating and adapting to environmental changes. The main objectives of the Planetary Health Cluster are to: 1. Promote and disseminate environment and health research from a Planetary Health perspective; 2. Raise awareness of the health impacts of environmental changes and the costs and benefits of mitigation and adaptation interventions; 3. Maximize the communication and dissemination of results through the projects’ networks; 4. Contribute to evidence-based decision-making and stronger EU and global policies; and 5. Build capacity around environment and health research.