This study investigated the effects of self-esteem, self-efficacy, and anxiety on the Korean language proficiency of immigrant adolescents. Rosenberg(1965)’s RSES, Kim & Park(2001)’s ASES, Horwitz et el.(1986)’s FLCAS, and Lee-Ellis(2009)’s Korean C-test were employed to conduct surveys with 79 immigrant adolescents in a high school. To analyze the data, frequency analysis, correlation analysis, regression analysis, and t test were used. The study found: (1) Immigrant adolescents had lower self-esteem, higher self-efficacy, and lower anxiety than any other language learners. Male immigrant adolescents preferred a higher task difficulty compared to their female counterparts. (2) Self-esteem and self-efficacy(self-confidence) were positively correlated with Korean language proficiency, and language anxiety was negatively correlated. (3) Self-esteem, self-confidence, and anxiety were factors affecting Korean language proficiency.