Background: Several studies have shown that religiosity has beneficial effects on health, mortality and pathological conditions; little is known about religiosity in Alzheimers disease and the progression of its cognitive, behavioral and functional symptoms. Our aim was to identify any relationship between religiosity and the progression of cognitive impairment and behavioral disorders in mild-moderate Alzheimers disease, and any relationship between the patients religiosity and the stress in caregivers. Materials and Methods: 64 patients with Alzheimers disease were analyzed at baseline and 12 months later using the Mini-Mental State Examination (MMSE), the Behavioral Religiosity Scale (BRS) and the Francis Short Scale (FSS). Caregivers were also questioned on the patients functional abilities (ADL, IADL), the behavioral disturbances (NPI), and on their stress (NPI-D, CBI). Patients were divided into 2 groups according to BRS: a score of < 24 meant no or low religiosity (LR), while a score of ≥24 meant moderate or high religiosity (HR). Findings: LR patients had worsened more markedly after 12 months in their total cognitive and behavioral test scores. Stress was also significantly higher in the caregivers of the LR group. Global BRS and FSS scores correlated significantly with variations after 1 year in the MMSE (r: 0.50), NPI (r:-0.51), NPI-D (r:-0.55) and CBI (r:-0.62). A low religiosity coincided with a higher risk of cognitive impairment, considered as a 3-point decrease in MMSE score (OR 6.7, CI: 1.8- 24.7). Interpretation: Higher levels of religiosity in Alzheimers dementia seem to correlate with a slower cognitive and behavioral decline, with a corresponding significant reduction of the caregivers burden.