Teams of unlicensed personnel and registered nurses have provided hospital-based nursing care for decades. Although ineffective teamwork has been associated with poor patient outcomes, little is known of the perspectives of nursing assistive personnel (NAP). The purpose of this study was to gain insights into the perceptions of NAP and professional registered nurses (RNs) on teamwork in acute care. In a qualitative descriptive approach in a metropolitan hospital in the southeastern United States, 33 NAP participated in audio-recorded focus group sessions, and 18 RNs provided responses to open-ended electronic survey questions. Findings were examined in relation to previously identified coordinating mechanisms of teamwork: shared mental models, closed-loop communication, and mutual trust. None of the mechanisms was strongly represented in these data. In contrast to RNs' mental models, NAP perceptions of teamwork included the centrality of holistic caring to the NAP role, functional teams as NAP-only teams, NAPs and RNs working in parallel spheres rather than together, and team coordination in silos. Closed-loop communication was less common than one-way requests. Mutual trust was desired, but RNs' delegation of tasks conveyed to NAP a lack of value and respect for the NAP role, while RNs perceived a professional obligation to delegate care to ensure quality of care amid changing patient priorities. Further empirical research into NAP practice is needed to enhance understanding of teamwork issues and direct effective interventions to improve work environments and ultimately patient outcomes. © 2016 Wiley Periodicals, Inc.