Background: Workplace-based assessment may be further optimized by drawing upon the perspectives of multiple assessors, including those outside the trainee’s discipline. Interprofessional competencies like communication and collaboration are often considered suitable for team input. Aim: We sought to characterize multidisciplinary expectations of communicator and collaborator competency roles. Methods: We adopted a constructivist grounded theory approach to explore perspectives of multidisciplinary team members on a clinical teaching unit. In semi-structured interviews, participants described expectations for competent collaboration and communication of trainees outside their own discipline. Data were analyzed to identify recurring themes, underlying concepts and their interactions using constant comparison. Results: Three main underlying perspectives influenced interprofessional characterization of competent communication and collaboration: (1) general expectations of best practice; (2) specific expectations of supportive practice; and (3) perceived commitment to teaching practice. However, participants seemingly judged trainees outside their discipline according to how competencies were exercised to advance their own professional patient care decision-making, with minimal attention to the trainee’s specific skillset demonstrated. Conclusion: While team members expressed commitment to supporting interprofessional competency development of trainees outside their discipline, service-oriented judgement of performance loomed large. The potential impact on the credibility of multidisciplinary sources for workplace-based assessment requires consideration.