e23015 Background: Interdisciplinary teams are an indispensable characteristic of modern organizations, particularly in healthcare settings that require specialists to work together to solve multifaceted patient care problems. Multidisciplinary tumor boards (TBs) aim to coordinate multidisciplinary perspectives to help the oncology team devise the best treatment program for the patient. Yet, while this is their purpose, studies have found that TBs do not always achieve that goal effectively. Why are some tumor board (TB) teams more effective than others? This study shed light on key characteristics found among highly effective TBs. It provides a theoretical explanation of their organizational behaviors and structures and their effect on cancer treatment decision-making. The research is grounded in organizational behavior theories that have historical prominence in group decision-making, social hierarchy, and interdisciplinary collaboration, and are used to explain the phenomenon under investigation best. Methods: Qualitative research was used in the study. Data from 44 different TB observations and 18 interviews were gathered over four years at seven research hospitals in the United States and United Kingdom. The data were then coded, analyzed and synthesized with organizational behavior theory to explain the social phenomena under investigation. Results: The study revealed that certain TBs practice strong collaboration displaying high levels of partnership, cooperation, equality, and interdependency, which was incorporated explicitly into their meeting systems to achieve their common goal. Team-based characteristics such as members’ consistent shared preferences and identity, coordinated interactions, a collective learning process, and shared power and partnership are key markers found within these teams that positively influenced treatment decision-making processes and outcomes, earmarking best practices in TB groups. Conclusions: Organizational theory that suggests that for a collaborative process to be effective, team-based mechanisms need to be adopted in which each member respects, trusts, and acknowledges the skills and expertise of other disciplines in the organization, shares team values, decision-making processes, responsibilities, and planning, relies mutually upon other team members, and works outside normal professional boundaries openly and willingly. In an egalitarian structure like that of the TBs reviewed in this study, where preferences and identities are consistent and groups are collaborative, treatment decisions are less biased and incorporate multidisciplinary perspectives. Thus, this study suggests that by possessing both team- and task-based characteristics and practices, TBs engage in best practices, and thereby optimize their functionality.