the purpose of the present study was to compare metacognitive beliefs and cognitive failures in older adults with and without religious behaviors. The method of the present study was causal-comparative. The statistical society was comprised of all older adults in Ardebil. The study sample included 235 older adults (112 older adults without religious behaviors and 123 older adults with religious behaviors), chosen by convenience Sampling. Data were collected using the Broadbent, Cooper, Fitzgerald and Parkes, cognitive failures questionnaire, Nielsen, religious behavior questionnaire and Wells and Certwright-Hatton, and metacognition questionnaire. The results of Multivariate analysis of variance (MANOVA) showed that the average scores of the components of cognitive trust, positive beliefs about worry and self-awareness in older adults with religious behaviors were significantly lower than the older adults without religious behaviors (p<0.01). But, between the average scores of metacognitive beliefs there is no significant difference in older adults with religious behaviors high and low. Also, the results of Multivariate analysis of variance (MANOVA) showed that there is a significant difference between the average scores of cognitive failures and its components (distractibility, memory lapses, Blunders and forgetting people’s names) in older adults with and without religious behaviors. In other words, average scores of the cognitive failures and its components (distractibility, memory lapses, Blunders and forgetting people’s names) were significantly lower in older adults with religious behaviors (p<0.01). This finding has important implications are regards the mental health of older adults.