Climate change is already having a significant impact, and Germany, the EU’s largest emitter of carbon dioxide, is experiencing this firsthand, prompting adaptation measures in cities. German companies must balance social and environmental responsibility with economic goals. Achieving sustainable business goals requires employee support and engagement, which can be facilitated through internal and external communication using storytelling and narratives. This paper addresses a gap in research on internal and external sustainability communication by examining both simultaneously. Using a semi-structured interview study, the paper examines the current state of sustainability communication in selected German companies, focusing on addressees, channels, structure, and content. The results revealed a high relevance of sustainability in companies, identified similarities between internal and external characteristics of communication, but also highlighted specific differences (e.g., with regard to communication strategies). This paper also identifies effects of communication and areas for improvement and suggests directions for future research to improve sustainability communication and its role in promoting a more sustainable society.