Diagnostic errors cause significant patient harm and occur among 15 percent of all clinical diagnoses, but research has yet to effectively target, prevent, and mitigate diagnostic errors from occurring. So far, literature has examined how diagnostician decision-makers perform and reach a clinical diagnosis individually. However, the impact of team-based activities on diagnosis is unknown. The purpose of this study is to describe provider perception on how providers come together as a team in order to complete a clinical diagnosis. As a qualitative descriptive study with overtones of grounded theory, 18 semi-structured interviews of medical intensive care unit providers were audio-recorded, transcribed, and coded generating themes of diagnostic teamwork structure and functioning. Diagnostic teams are described using themes of inter-professional and intra-professional teamwork among roles with and without diagnostic team identity. Novel approaches to diagnostic error research, practice implications for current providers, and applications provided for improving education and team training. By providing preliminary insights on the role of teamwork in diagnostic decision-making, this study may assist future studies that improve diagnostic teamwork and prevent diagnostic errors.