AIMS: Bone and joint infection in children can result in bone and joint damage, sepsis, and even death. Diagnosis is informed by the history, examination, and a suite of tests, including blood markers, radiographs, ultrasound, and MRI. This study aimed to identify the communication needs of families during diagnostic assessment of bone and joint infection. METHODS: This was a qualitative study involving semi-structured interviews with children and families who had experienced diagnostic tests for bone and joint infection, and health professionals experienced in the care of affected children. A total of 21 families (four children; 21 parents) and 11 health professionals from 11 English and Welsh hospitals were interviewed. Data analysis was informed by thematic analysis. RESULTS: Families often felt highly anxious during diagnosis. Some described a disorderly diagnosis process, gaps or inconsistencies in information, and insensitive communication that contributed to their anxiety. Other families described more positive experiences, indicating how health professionals helped them feel prepared by providing an outline of timelines, the rationale for tests, and the potential need to adjust plans as new information became available. Participants recognized the importance of age-appropriate communication with children, and the involvement of play specialists in this process. CONCLUSION: The findings demonstrate the intense anxiety families experience during assessment of bone and joint infection, particularly when they are left to make sense of uncertainties by themselves, or when communication is unclear. Health professionals can support families during diagnosis by attending to both the information they provide and how it is provided, while acknowledging the uncertainties of the diagnosis process. Specifically, families valued explanations of the rationale for different clinical investigations and their timing, and advance discussion of the next steps and possible outcomes of diagnostic testing. When test results became available, families were also helped by clear follow-up plans, including in situations when the results were inconclusive.