Abstract: Background: Care coordination is considered important for patients with rare conditions, yet research addressing the impact of care coordination is limited. This study aimed to explore how care coordination (or lack of) impacts on patients and carers. Semi-structured interviews were conducted with 15 patients and carers/parents in the UK, representing a range of rare conditions (including undiagnosed conditions). Transcripts were analysed thematically in an iterative process. Results: Participants described a range of experiences and views in relation to care coordination. Reports of uncoordinated care emerged: appointments were uncoordinated, communication between key stakeholders was ineffective, patients and carers were required to coordinate their own care, and care was not coordinated to meet the changing needs of patients in different scenarios. As a result, participants experienced an additional burden and barriers/delays to accessing care. The impacts described by patients and carers, either attributed to or exacerbated by uncoordinated care, included: impact on physical health (including fatigue), financial impact (including loss of earnings and travel costs), and psychosocial impact (including disruption to school, work and emotional burden). Overall data highlight the importance of flexible care, which meets individual needs throughout patients’/carers’ journeys. Specifically, study participants suggested that the impacts may be addressed by: having support from a professional to coordinate care, changing the approach of clinics and appointments (where they take place, which professionals/services are available and how they are scheduled), and improving communication through the use of technology, care plans, accessible points of contact and multi-disciplinary team working. Conclusion: This study provides further evidence of impacts of uncoordinated care; these may be complex and influenced by a number of factors. Approaches to coordination which improve access to care and lessen the time and burden placed on patients and carers may be particularly beneficial. Findings should influence future service developments (and the evaluation of such developments). This will be achieved, in the first instance, by informing the CONCORD Study in the UK.