Purpose: The purpose of this study is to examine depression levels of some Korean mothers of preschool children and to find out how much influence their psychological, parenting and relational characteristics have on their depression. Methods: This study has been conducted to analyze depression-related and -influencing factors of the Korean mothers of preschool children [7th Panel Study of Korean Children (2014)]. Correlation analysis has been used to examine the relationship between the mothers' psychological, parenting and relational factors and their depression. Hierarchical analysis has been employed to clarify the factors associated with depression. Results: Hierarchical regression analysis has found out that the significant predictors of the depression of the Korean mothers of preschool children include age, educational and employment status, monthly income, smoking status in Model 1. The significant variable is self-esteem in Model 2, parenting stress in Model 3, and, lastly, marital conflict in Model 4. Conclusion: Through this study, it has been discovered that the psychological characteristics of the Korean mothers of preschool children are the most influential factor affecting their depression. The results suggest that it is necessary to develop a community program for improving self-esteem and reducing parenting stress of Korean mothers of preschool children in their parenting.