Objective : The objective of this study was to investigate the effect of a tailored cognitive training program using Brain Training on cognition, depression, and activities of daily living(ADL) for the elderly with cognitive impairment attending a Day care center. Methods : The subjects of the study were the elderly aged 65 years and older who had been diagnosed with mild cognitive impairment or mild dementia and attended N Day care center in Busan Metropolitan City in South Korea. The study was conducted from August 3 to October 4, 2023. A tailored cognitive training program was conducted with 18 research participants, who were divided into two subgroups based on the level of KDRS-2. The two subgroups included a supplementary group consisting of 8 people, and an in-depth group of 10. The program was implemented with the two groups 11 times: 3 times a week for 4 weeks, with each session lasting 60 minutes. To analyze the effectiveness of the tailored cognitive training program, before and after the program, the Korean Dementia Rating Test Scale-2(KDRS-2), Patient Health Questionnaire-9(PHQ-9), Seoul-Activities of Daily Living(S-ADL), Seoul-Instrumental Activities of Daily Living(S-IADL) evaluation was conducted. The collected data were analyzed using descriptive statistics and Wilcoxon signed-rank test. Results : After the intervention, PHQ-9 scores and S-IADL scores significantly decreased in the supplementary group(p<.05; p<.05). In the in-depth group, KDRS-2 score significantly increased(p<.05) and S-IADL score significantly decreased(p<.05). Conclusion : These findings confirm that a tailored cognitive training program was effective in improving cognitive function and IADL and alleviating depression in the elderly attending a Day care center, thereby proving the effectiveness of a cognitive training program tailored to individual cognitive levels.