Background: Little is known about how Australian national safety standards for communicating multidisciplinary care are operationalised during high-risk care transitions. We examined transfer of care for complex patients from the emergency department (ED) to medical wards to explore nurse-to-nurse communication about multidisciplinary care provided in the ED. Methods: Using naturalistic, mixed-methods design, observation, audit and interview data were collected from a convenience sample of 38 nurses during transfer of care for 19 complex patients from the ED to medical wards at a tertiary hospital. A focus group with 19 clinicians from multiple disciplines explored explanations for findings and recommendations. Quantitative data were analysed using frequencies and descriptive statistics; the Connect, Observe, Listen, Delegate (COLD) framework informed qualitative content analysis. Results: Nurses seldom communicated multidisciplinary care at patient transfer. Most handovers included Connect and Observe (63–95%) and Listen (90%); Delegate (42%) behaviours were infrequent. Behaviours consistent with good practice recommendations (90%) and known to increase communication risk (53%) were observed. Tensions between policies and clinical processes, and information quality negatively impacted transfers. Conclusions: This study revealed gaps in nurse-to-nurse communication about patients’ multidisciplinary care. Complex factors negatively impact nurses’ handover communication necessitating workarounds, and highlighting nurses’ role as patient safety advocates.