Prior research shows that supervisors of teacher candidates are typically underprepared for their work and receive little oversight of it. However, there has been less research into these causes and the effects of minimal preparation on supervisors. This case study of a teacher education department uses survey, interviews, and document analysis to examine the tensions that occur when supervisors are underprepared for their roles. The results indicate three tensions that undermine supervisors' practice: unclear expectations, perfunctory evaluations, and the failure to develop teacher educator identities. In the absence of organizational supports for supervisor preparation and development, supervisors relied on peer networks and their PK-12 experience to inform their practice. Program administrators lamented the lack of training for supervisors but did not have the time or resources to support it. Intentional preparation could help supervisors navigate these tensions and should aim to align supervisors' training to the roles they embody.