To effectively mitigate the health impacts of climate change, future nurses must be equipped with the requisite knowledge and competencies. Knowing their levels of eco-literacy would help to make them more effective. Background/Objectives: This descriptive study will use a three-round, multicentre, modified e-Delphi survey to establish an expert panel’s consensus on the Climate, Health, and Nursing Tool’s (CHANT) item-level and scale-level content validity indices. It will also examine potential associations between the expert panel members’ sociodemographic and professional characteristics and their content validity index assessments of the CHANT. Methods: The study will be conducted in the French-speaking regions of Switzerland, running its three-round e-Delphi survey between January and April 2025. After each round, the CHANT’s overall scale-level and individual item-level content validity indices will be computed. Comparisons between different types of healthcare professionals’ profiles will also be conducted. Results: The three-round modified e-Delphi survey should allow the expert panel to reach a consensus on the CHANT’s overall content validity index. The tool should then be considered suitable for pilot testing. The first round brought together 16 experts from different regions, namely French-speaking Switzerland, France, and Belgium. Conclusions: To ensure that the nursing discipline is well positioned to meet future challenges, the development of eco-literacy must be integrated into nursing education. Ensuring the CHANT’s conceptual and psychometric validity will be essential in strengthening nursing competencies in and knowledge about planetary health and in implementing future educational interventions.