Abstract Aim This study aimed to assess the knowledge, attitudes, and practices (KAP) of physicians in Japan toward climate change and health, their delivery of climate-specific advice to patients, and their advocacy for climate change policy. Subject and methods This cross-sectional study included licensed physicians active in clinical practice in Japan. Data were collected through a web-based platform from November 21 through November 27, 2023, using a 32-item self-administered questionnaire. Results A total of 1100 physicians with a mean age of 51.2 years (SD11.9) were included in the analysis. More than half (56.7%) agreed that physicians should advise their patients on the links climate change has on their health; however, less than half (32.6%) of the physicians responded that they do. Among the factors that reduced their action to deliver climate-specific health advice and advocacy were a lack of information/resources and knowledge. The multivariable logistic regression model showed that having prior climate change education or training, knowledge, and awareness is associated with physicians’ delivery of climate-specific advice to patients and advocating for climate change policy. Conclusion Many physicians recognize their responsibility to educate their patients on the impact climate change has on their health. There is a significant gap between the physicians’ willingness and what happens in practice. Among the main factors that reduce their action to engage in delivering climate-specific health advice and advocacy were a lack of information/resources and a lack of knowledge. Physicians need to be better equipped with the education, resources, and support to apply their expertise and influence to combat climate change.