While it is widely understood that assessment policy and its implementation by actors profoundly affect the quality of student learning in higher education, there is a dearth of research highlighting the institutional factors that influence policy implementation in today’s globalized world. Although leadership is an often-cited factor influencing policy implementation, it is not well understood in the United Arab Emirates (UAE) and the Middle East. This paper discusses a qualitative case study that explored how leadership negotiates institutional factors and influences actors’ implementation of assessment in a Health Sciences department in an institution in the UAE. Adopting Hans Bresser’s (2004) Contextual Interaction Theory (CIT) as an empirically-based conceptual framework, the case study examined how institutional factors and leadership influence motivation, cognition, and power/capacity in a UAE institution. Data were collected from semi-structured interviews with key informants in a Health Sciences department and internal and external policy documentation. Findings indicated that the policy design and the institution’s top-down approach to governance influenced leaders’ implementation of assessment policy in particular ways. In addition, the institutional culture of change and the sizable multi-campus structure impacted the department's policy and leaders’ assessment implementation. Finally, there were findings on the nature of leadership and the nuances of supporting and influencing policy implementation that was contextualized in UAE society. The study results offer policymakers, institutional leaders, and department-level leaders (department and program leaders) a deeper understanding of how system-level influences impact policy implementation.