Organizations implementing enterprise resource planning (ERP) systems experience the need for extensive changes in structure, core processes, and roles - making change management crucial. Prior research on change management in ERP implementations focuses mostly on large enterprises and lacks empirical insight into why change management is challenging. We conducted a case study in a Norwegian Small and Medium-sized Enterprise (SME) working in mechanical manufacturing. Interviews, observations, and documents were analyzed. This study contributes to the literature focusing on change management in ERP implementations and pro-vides rich insight into how and why change management is challenging in an SME context by detailing eight key reasons behind 33 challenges. Lessons learned from this study may have transferable value to other SMEs implementing ERP. The study highlights the importance of considering culture, overall organizational workload, and ensuring deep engagement during an ERP project. Several of the challenges were interconnected. Customizing organizational processes was challenging because it opposed the established culture within the company, risk management was underestimated, and culture was more of an impediment than a facilitator for change management. Finally, the management style, lack of holistic project view, and lack of competence in computer usage were also identified as challenges impeding an efficient implementation.