X-linked hypophosphatemia (XLH) is a rare genetic disorder that leads to rickets, osteomalacia, and other skeletal abnormalities. Many people with XLH get support from informal caregivers, often family members, to help with their daily living. Although generally rewarding, being a caregiver can be associated with extra physiologic, physical, and mental health burdens, which are poorly researched and understood. This study aims to investigate the quality of life of people with XLH who are also caregivers of relatives with XLH. To do this, we conducted a cross-sectional study to characterize the quality of life of caregivers using both a caregiver-specific and a generic quality of life questionnaire, examined the association between the instruments for caregivers, and compared the generic quality of life between caregivers and matched non-caregivers. We used data from the Rare UK Diseases Study (RUDY), whose platform allows people with XLH to record their own characteristics and outcome measures, including the caregiver oncology quality of life questionnaire (CarGOQoL) and the generic EQ-5D. Caregivers and non-caregivers with XLH were matched on gender and age. Caregivers (n = 13) report not feeling burdened or seeing their self-esteem impacted by providing care, but their private life, leisure, and psychological well-being were affected. They report worse quality of life than the UK general population. CarGOQoL and EQ-5D were highly correlated (p < .001). Caregivers of people with XLH reported better quality of life than non-caregivers in all EQ-5D dimensions except for Anxiety/Depression (EQ-5D score of 0.467 vs 0.356 for non-caregivers). Our findings must be interpreted with caution, given the small sample size, although they are consistent with the literature. Caregivers play an important role in supporting the everyday life of those they look after. This role should be recognized, and helpful information and tools made available to support them in that process.