This study aims to determine the effect of brain gym on decreasing the level of dementia and depression in the elderly in the Health Center Community of Mulyorejo in Deli Serdang Regency. The population of this study was 5765 elderly people. The sampling technique uses the Slovin formula and it is determined through inclusion criteria using a purposive consecutive method so that the total sample of 30 respondents is divided into two groups, 15 respondents with dementia and 15 respondents with depression. A quasi-experimental pre-post test design was used, where a control group wasn't used, then a pre-test is followed by intervention in each group and at the end a post-test in each group was conducted. Data analysis used the Wilcoxon test due to the unusual distribution of the data. The results of the study on the dementia variable obtained p-value (p = 0.000 <0.05) and the depression variable value (p-value = 0.006 <0.05), so it can be concluded that the brain gym has an effect on decreasing the level of dementia and depression in the elderly. The use of brain gym can be one of the considerations in nursing intervention as a complementary therapy to reduce the level of dementia and depression in the elderly, and is expected to be carried out routinely during the activities of the elderly of each Posyandu (integrated health care center).