BACKGROUND: Clinical and support staff in modern general practice must work across in-person and digital modalities to deliver high-quality, safe care in a context of high workload, constant change, and intermittent crisis. Navigating this environment is cognitively and emotionally demanding, and requires complex teamwork. Staff morale may often be low, and staff turnover high. AIM: To understand how the context of modern UK general practice affects staff wellbeing and teamwork, and to develop our understanding of how to improve these aspects of work culture. DESIGN AND SETTING: This paper reports on a multi-sited case study of 10 general practices across England, Wales, and Scotland. METHOD: Multiple qualitative methods, including ethnographic observations, interviews, and focus groups, were used to develop case studies. First, we conducted in-depth longitudinal case studies of two practices focused on developing theory, which we cross-compared with eight other, more focused case studies. Our analysis was informed by theories from organisational research, including psychological safety, relational coordination, and attentional infrastructure. RESULTS: Staff wellbeing and effective teamwork depended on positive team relations. Practices in which such relations were valued and nurtured (that is, those with a strong relational infrastructure) appeared to have stronger team identities, better coordination of work tasks, and higher overall staff wellbeing than those in which team relations were not actively nurtured. Staff relations were built and sustained through various individual actions and organisational routines. CONCLUSION: This study has identified several elements of 'relational infrastructure' with the potential to improve team relations, communication, and coordination, which may also enhance practices' resilience to withstand change and crises.