According to literature, religious attitudes can enhance cognitive functioning in elders, because it gives the sense of purpose in life. Therefore, due to the controversy among studies, it is of great importance to identify whether religiosity levels are greater in cognitively intact elders compared to participants with MCI as well as in patients with mild dementia irrespective etiology. This study aims to examine possible differences with regards to religiosity levels between controls, MCI and patients with mild dementia. Religiosity was measured using the Systems of Belief Inventory (SBI-15R, Holland, et al., 1998), which was standardized in Greek population. According to the ANOVA test, significant main effect was found for group by means of SBI-15R score F(2, 400) = 5.624, p = .004, η2 = .027. Post-hoc comparisons showed that MCI participants had significantly higher total religiosity scores (M = 35.48, SD = 9.67) compared to the healthy controls (M = 31.73, SD = 4.11), p = .002. Additionally, patients with mild dementia had also increased religiosity scores (M = 35.13, SD = 9.09) compared to controls (M = 31.73, SD = 4.11), p = .010. Additionally, Pearson correlation showed significant relationship between GDS with SBI-15R score (r = -.221 p = .023) and Religious beliefs & practices subscale (r = -.260 p = .007) in patients with mild dementia. Results suggested that MCI participants as well as patients with mild dementia demonstrated higher religiosity levels compared to the healthy controls. Moreover, the total religiosity levels were related with depressive symptomatology only in patients with mild dementia unlike to the other two groups.