Background: Depression has been shown to negatively impact clinical outcomes, increase health care utilization, and raise medical care costs among affected individuals. Prior research suggests that the emergency department (ED) is highly utilized by depressed patients due to various factors such as existing age, sex, and chronic conditions. Identifying depression severity groups at higher risk of utilizing the ED may provide greater opportunity to improve patient health outcomes and increase care quality. Methods: A non-concurrent cohort study was conducted on 18,574 adult patients at Kaiser Permanente Napa-Solano service area who were screened for depression (through the Patient Health Questionnaire-9) in 2016-2017. Extracted data included: age, sex, race/ethnicity tobacco use, and several chronic conditions. Using descriptive statistics, bivariate analysis, and multivariate negative binomial regression, statistical associations between depression severity (most recent PHQ-9 score in 2016-2017) and ED utilization (number of ED visits from 2017-2018) were examined. Results: The study population was primarily female (68%) and over the age of 41 years (60%). 58% of patients identified as Non-Hispanic White while the remaining 42% consisted of minorities. 22.4% of patients had moderately severe/severe depression. After adjusting for several factors, we found that patients with moderately severe/severe depression had statistically significantly more ED visits (incidence rate ratio = 1.22, 95% CI = 1.064 – 1.396) than patients without depression. Conclusion: Frequent ED utilization among severely depressed patients may be addressed through the evaluation of barriers to depression screening and treatment and improvement of care coordination between Emergency, Family Medicine, and Behavioral Health Departments.