Purpose: Although it is known that depression is highly prevalent in institutionalized older adults, little is known about its predictors in long-term care facility in Korea. The aim of this study was to identify the predictors of depression among institutionalized older adults. Methods: This study was a secondary analysis of a large data set which was used in a cross-sectional research method conducted in seven geriatric long-term care facilities located in Seoul, Kyunggi-do, and Kangwon-do, Korea. The participants were 305 older adults over 65 years old. Data were collected during November and December, 2011, using structured questionnaires which included general characteristics, cognitive function, and depression. Data analysis included descriptive statistics, t-test, one-way ANOVA, and logistic regression. Results: Mean age of the participants was 80.38±7.14 and 38.7% of the participants presented symptoms of depression; 24.3% showed minor depression and 14.4% showed probable major depression. Depressive symptoms were related to insomnia, delirium/confusion, bad eyesight, bad communication, and limb impairment. Insomnia (OR=5.94; 95% CI=3.31~10.64) and delirium/confusion (OR=4.77; 95% CI=2.24~10.20) were the significant predictors of depression among institutionalized older adults. Conclusion: Nursing interventions should be developed considering the factors of insomnia and delirium/confusion to decrease depression in this population.