In this study, we assessed the mental health of Korean call center employees and investigated the potential predictors of their mental health status. A cross-sectional study using self-completing questionnaire was conducted for employees working for a credit card call center. A total of 306 call center employees completed the Depression Anxiety Stress Scale, the Emotion Labor Scale, and the Korean Occupational Stress Scale. The results showed that more than half of the participants reported high levels of depression, anxiety, and stress. A multiple regression analysis indicated that the total scores on the Depression Anxiety Stress Scale were predicted by perceived health, job satisfaction, job demands, organizational injustice, and emotional dissonance suggesting that, in the interest of improving the mental health of call center employees, their job demands and emotional dissonance should be reduced and the work environment be improved. Consideration should be given to providing routine assessments of mental health, including depression, anxiety, and stress, and the corresponding need for the development of an intervention program and other work-related policies that would protect employees from the risk of poor mental health outcomes.