This paper explores environmental sustainability in the field of sport. Behaviour toward environmental sustainability can be influenced by nature experiences. We investigate how physical education (PE) teachers’ nature experiences contribute to their environmental identity by employing the pedagogical model of education for sustainability as a framework to analyze nature drawings, individual interviews, and focus group discussions. We investigate PE teachers in Sweden and Switzerland, countries sharing similar general curricula formulations on sustainable development but differing in PE curricula. The Swiss participants display a sport-focused interpretation of nature, likely due to sport-related experiences in PE teacher education. Conversely, Swedish participants exhibit transformative nature experiences with more focus on nature than on activities, fostering an environmental identity where they perceive themselves as part of nature. These findings contribute to the understanding of the role of nature experiences in PE teachers’ environmental identity development and its potential contribution to environmental sustainability in education.