More sustainable environmental behavior and management is necessary if we are to sustain human well-being; however, current educational practices are not well aligned to support the development of environmentally informed citizens, including adequate teacher preparation. Classroom teachers are in a unique position to develop student skills and knowledge for sustainable environmental behavior through their teaching. Yet, teachers report a gap in their understanding of social-ecological systems, which presents a barrier to developing environmental citizens, or those enacting the skills and knowledge necessary for sustainable environmental behavior. This study focuses on the impact of a teacher professional development workshop designed to develop teachers' understanding of local social-ecological systems. We explore the effects of the workshop through the framework of environmental citizenship which has five components: Ecological Literacy, Civics Literacy, Self-Efficacy, Values Awareness, and Practical Wisdom. The quasi-experimental design included a pre- and post-survey of teacher participants' environmental citizenship. The Wilcoxon signed-rank test showed that the median posttest scores were significantly higher than the median pretest scores, indicating a statistically significant increase in environmental citizenship for all five components. The environmental citizenship of teachers has not been reported in the literature, despite the emerging importance of environmental citizenship dispositions for delivering social-ecological systems content. Although the nature of the study limits our ability to generalize beyond this case, our findings suggest that environmental citizenship may increase as a result of teacher professional development, with potential to inform the type of education that leads to fostering environmental citizenship in students.