Introduction Informal caregivers of patients with Alzheimer disease (AD) have a poor health-related quality of life (HRQOL). HRQOL is an increasingly common user-focused outcome measure. We have evaluated HRQOL longitudinally in caregivers of AD patients at baseline and at 12 months. Methods Ninety-seven patients diagnosed with AD according to the NINCDS-ADRDA (National Institute of Neurological and Communicative Disorders and Stroke, and Alzheimer's Disease and Related Disorders Association) and their 97 respective primary caregivers were included in the study. We analysed the following data at the baseline visit: sociodemographic data of both patients and carers, patients’ clinical variables, and data related to the healthcare provided to patients by carers. HRQOL of caregivers was measured with the SF-36 questionnaire at baseline and 12 months later. Results At 12 months, primary caregivers scored lower in the 8 subscales of the SF-36 questionnaire; differences were statistically significant in all dimensions except for ‘physical function’ and ‘social function’. Baseline scores in our sample were lower than those of the general population. ‘Vitality’ is the dimension that presented the lowest scores. Conclusion HRQOL in caregivers of patients with AD deteriorates over time and is poorer than that of the age- and sex-matched general population.