The purpose of this study was, conducted with experimental design, to investigate the effect of reminiscence therapy on cognition, depression, activities of daily living of institutionalized mild and moderate Alzheimer patients. The study was conducted with a total of 62 patients (31 intervention group and 31 control group) in four home care in Ankara, Turkey. Study was done between the July 1, 2013 and December 20, 2014. Reminiscence therapy sessions were held with groups consists of 4-5 patients, once a week with 30-35 minute duration for 12 weeks. Standardized Mini Mental Test was used in sample selection. Patients were listed through their mini mental test scores, and randomized as odd numbers to control group and even numbers to intervention group. Data were collected with forms developed by researcher Data Sheet' and Activities of Daily Living Follow-up Form' as well as scales Standardized Mini Mental Test' and Geriatric Depression Scale'. Chi-square, Mann Whitney-U test, variance analyses in repeated measures and Bonferroni tests were used for analysis. The increase in mean Standardized Mini Mental Test score and the decrease in mean Geriatric Depression Scale score of the individuals in the intervention group compared to the control group at the end of the reminiscence therapy was statistically significant (P < 0.05). At the end of reminiscence therapy sessions, increase in cognition and decrease in depression were found statistically significant in intervention group.