Cross-sectional studies report notable discrepancies between patient and caregiver ratings of the quality of life of patients (QoL-p) with Alzheimer"s disease (AD). This study aimed to identify the factors associated with any changes in QoL-p ratings and any discrepancies between patient and caregiver ratings of QoL-p. Three-year follow-up of a cohort of non-institutionalized patients (n = 119). QoL-p was assessed by the Quality of Life in AD (QoL-AD) scale. We analyzed the influence of functional and cognitive status and behavioral problems in patients, and burden and mental health in caregivers. Repeated measures analysis was applied to the scores of patients and caregivers on the QoL-AD, and to the discrepancies between them. Generally, patients" own ratings remained stable over time (F 3,116 = 0.9, p = 0.439), whereas caregiver ratings showed a decline (F 3,116 = 9.4, p < 0.001). In the analysis of discrepancies, patients with anosognosia gave higher ratings (F 1,117 = 11.9, p = 0.001), whereas caregiver ratings were lower when the patient showed greater agitation (F 1,117 = 13.0, p < 0.001), apathy (F 1,117 = 15.4, p < 0.001), and disabilities (F 1,117 = 17.1, p < 0.001), and when the caregiver experienced greater burden (F 1,117 = 9.0, p = 0.003) and worse mental health (F 1,117 = 10.1, p = 0.003). Patient ratings of QoL-p remain generally stable over time, whereas those of caregivers show a decline, there being significant discrepancies in relation to specific patient and caregiver factors.