The purpose of the study was to investigate the impact of maternal stress as it relates to the mothers' perceived social behaviors of their preschool children in both immigrant Korean families in the US and Korean families in Korea. The subjects included 49 immigrant Korean mothers in the US and 52 Korean mothers in Seoul, Korea. This study is relevant to current research because of the dramatically increasing Korean immigrants in the US and needed information concerning unique cultural and psychosocial needs of Korean-Americans. All mothers completed the Demographic Survey, Parenting Stress Index (PSI), and Preschool and Kindergarten Behavior Scales-2 (PKBS-2). Statistical analyses of the data used for the study were multiple regressions, independent t-tests, and Pearson correlation coefficients. Data analysis revealed that (a) there were different demographic variables affecting maternal stress between immigrant Korean mothers in the US and Korean mothers in Korea; (b) there was no significant difference in maternal stress and mothers' perceptions of their preschool children's social skills in the areas of social cooperation, social interaction, and social independence between both groups; (c) there was a significant difference in preschool children's behavioral problems in the areas of externalizing and internalizing social-emotional behaviors between both groups; (d) there was a negative relationship between maternal stress and mothers' perceptions of their preschool children's social skills, and (e) there was a positive relationship between maternal stress and mothers' perceptions of their preschool children's behavioral problems in both groups. Findings from this study showed that US immigrant Korean children and their mothers could experience stress in mother-child interaction and culturally expected gender behaviors. This study provides information that could be helpful for early childhood educators who work with Korean young children and their families in regards to the process of acculturating to the United States.