Climate change is one of the greatest health threats, yet many medical schools fail to adequately teach students about its impact. This article describes the development and implementation of an online elective in planetary health education. The online elective was designed for medical students in the clinical study term and delivered in a blended learning format. It features presentations, lectures, and transformative online teaching methods including a flipped classroom with final reflection, peer role-play for simulation of climate-sensitive health counseling, producing infographics, and problem-based activities. A pre-/post-course survey was conducted at the medical faculty of Goethe University Frankfurt for the years 2021 to 2024 and used to assess how effectively the elective contributed to participants' knowledge, beliefs, behaviors, and attitudes about the impact of climate change on health. Overall, participants rated the elective extremely positively. They were very satisfied with the design and content of the elective. The course effectively enhances self-reported knowledge of climate-related health effects and management while strengthening students' confidence in their role in climate protection. Intentions to apply new knowledge in medical practice and in one's own daily life significantly increased. Participants recommended incorporating the topic into the regular curriculum. The success of this pilot is evidence in favor of integrating climate change-related health topics into the medical curriculum, while the results provide insights useful to future research and development of online planetary health courses.