This article describes how trust among team members and in the technology supporting them was eroded during implementation of an electronic health record (EHR) in an adult outpatient oncology practice at a comprehensive cancer center. Delays in care of a 38-year-old woman with high-risk breast cancer occurred because of ineffective team communication and are illustrated in a case study. The case explores how the patient's trust and mutual trust between team members were disrupted because of inaccurate assumptions about the functionality of the EHR's communication tool, resultant miscommunications between team members and the patient, and the eventual recognition that care was not being effectively coordinated, as it had been previously. Despite a well-established, team-based culture and significant preparation for the EHR implementation, the challenges that occurred point to underlying human and system failures from which other organizations going through a similar process may learn. Through an analysis and evaluation of events that transpired before and during the EHR rollout, suggested interventions for preventing this experience are offered, which include: a thorough crosswalk between old and new communication mechanisms before implementation; understanding and mitigation of gaps in the communication tool's functionality; more robust training for staff, clinicians, and patients; greater consideration given to the pace of change expected of individuals; and development of models of collaboration between EHR users and vendors in developing products that support high-quality, team-based care in the oncology setting. These interventions are transferable to any organizational or system change that threatens mutual trust and effective communication.