Cross-company networking is essential to successfully implement Industry 4.0. In this context, numerous new demands on suppliers arise leading to integration challenges that require specific integration strategies. While these topics are important in business practice, an aggregated holistic overview is still missing. Therefore, this article examines new demands on suppliers, challenges in the implementation process, and integration strategies for supplier integration in the context of Industry 4.0. Expert interviews with 15 different industrial companies from the sectors mechanical and plant engineering, electronics and electrical engineering, automotive, and information and communication technology serve as an empirical basis. This study provides insights into the challenges and strategies of supplier integration, helps academia to understand this topic, and indicates need for future research. Furthermore, this paper develops implications for corporate practice in the area of supplier management.