The purpose of this review is to look at racial/ethnic disparities in the diagnosis of depression and its treatment and to explain the dynamics and causes of these racial/ethnic disparities in depression by looking at several theories, such as perceived racism, cultural competency, and other theories. Perceived racism is that the perceptions of an environmental stimulus as being racist affects the coping responses of ethnic/racial minorities, which alters psychological and physiological stress responses, and finally affects health outcomes negatively. A lower level of cultural competence can lead to health disparities. In addition, lower socioeconomic status and health care providers' beliefs and behaviors about patients' race/ethnicity and class can affect depressive symptoms as well as diagnosis and treatment. In order to reduce these racial/ethnic disparities in depression, diverse interventions should be developed to improve depression outcomes for ethnic minority populations based on these theoretical perspectives.