Teams operating in isolated, confined, and extreme (ICE) environments are especially rare and difficult to study. Their inaccessibility limits our understanding of the team processes driving effective functioning in ICE environments and our ability to support them. Contributing to this research space, we present a qualitative study of nine teams each deployed to Antarctica during the summer season for approximately six weeks. By analyzing participants’ daily journal entries reflecting on their teamwork and experiences, we generate an ecological model of extreme team functioning. Our model integrates individual, team, leadership, and contextual characteristics and processes to demonstrate how team functioning is often idiosyncratic and emerges from co-evolving relationships within and across levels. Our dynamic perspective helps move beyond the input-process-output organizing heuristic that has guided teams research for decades, but is limited in its ability to provide insights for specific teams. We take an idiographic approach to focus on understanding the unique processes of specific teams to provide insights into how to support a particular team and better direct interventions. Importantly, we find that the social relationships within the team are especially pertinent for determining team functioning in this ICE environment and identify team structures that supported positive psychosocial functioning and the role of leadership in fostering those structures. We discuss implications for future research and suggest teams in extreme environments can be better supported through special attention to the idiosyncratic processes of a given team and ensuring their social lives are considered alongside their taskwork.