The connections between climate, environment, and health as well as the concept of planetary health need to be integrated into the education of health professionals, as is increasingly demanded both internationally and nationally. Planetary health education should also aim to foster transformative action for climate protection and sustainability. In recent years, innovative teaching formats and objective catalogues have emerged internationally. In Germany, these topics have not yet been integrated into medical education everywhere. Since 2021, the Faculty of Medicine in Würzburg has offered an elective course as a first step of a longitudinal curriculum currently in development. The design, content, structure, and results of the evaluation are discussed in this article and will be used for quality assurance as well as the (further) development of this kind of educational interventions elsewhere. We developed an elective course for students in their second to tenth semester with 30 onsite and online face-to-face teaching units and an additional project phase. We used an innovative mix of didactic methods with online simulations, training in climate-sensitive health counselling, and interdisciplinary climate communication as well as local sustainability projects in small groups, with a large amount of peer-teaching. A quantitative and qualitative evaluation was done immediately after the teaching units through feedback rounds and online with the evaluation software Evasys®, using closed and open-ended questions exploring learning progress (summer semester) and achievement of learning objectives (winter semester), motivation to participate, acceptance of teaching methods, attitudes, relevance, and further interest. The evaluation questionnaire was slightly modified for the winter semester. In the summer and winter semester of 2021/2022, a total of 34 students (17 per semester) participated in the elective course; of these, 33 participated in the written evaluation. The evaluation in the summer semester (n = 17) showed a significant increase in self-assessed learning gain, the evaluation in the winter semester (n = 16) indicated a substantial achievement of learning objectives (mean = 3.96 of a 5-point Likert scale). Participants of both semesters (n = 33) regarded peer-teaching as a suitable method (mean = 4.2) and well-implemented (mean = 4.3). The topics were considered highly relevant but not adequately integrated into the main curriculum. There was a high level of interest in local impacts of climate and environmental changes and local measures for climate protection and sustainability. The specific projects in small groups may serve as examples of how transformative action can be promoted in education. In the current dynamic development of the widely demanded integration of planetary health education into curricula, this elective course shows a possible and well-accepted example with a combination of various innovative didactic methods aiming at the levels of knowledge, attitudes, skills, and self-efficacy (or confidence) alike. The positive evaluation by the students and the high interest in local sustainability projects show the potential for future integration into the main curriculum. The elective can serve as an inspiration to tackle the challenge of taking the steps from knowledge to action in planetary health education. While an elective cannot replace the integration of all relevant aspects of planetary health into the main curriculum, it can serve as a space for piloting of future curricular educational interventions and offer opportunities for developing transformative competencies.