The aim of this study was to assess whether family members perceive health-related quality of life (HRQoL) of family members with rheumatic illnesses differently from the perceptions of these patients themselves. Cross-sectional study of consecutive patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and ankylosing spondylitis (AS) attending two outpatient rheumatic clinics. HRQoL was assessed using the Spanish version of the World Health Organization Disability Assessment Scale (WHODAS-II) questionnaire; the "proxy" version is available for relatives. All patients and one proxy per patient separately answered the questionnaire at the clinic. Differences were determined by coefficients of determination (r (2)), Z scores, and meaningful differences of 30 %. Two hundred and ninety-one patients (111 SLE, 100 RA, and 80 AS) and their respective proxies were included. The mean age was 35 ± 13 years in SLE, 49.5 ± 14 years in RA, and 40 ± 14 years in AS patients. Divergent perceptions between patients and their proxies were found in 57 % of the SLE group, in 69 % of the RA group, and in 47 % of the AS group as per WHODAS-II global score. Stronger disagreement occurred for all the three groups in domains representing cognition and interaction with other people: around 60 % in the SLE group, 80 % in the RA group, and 40 % in the AS group. A substantial proportion of family members perceived the HRQoL of rheumatic family members differently from the perception of the patients themselves, most of the time biased toward underestimation, suggesting problems in the dynamics of efficient communication and social support.