This study examined the mediating effect of internal locus of control in the relationship between family and friend support and acculturative stress of North Korean adolescent refugees. Participants consisted of 101 North Korean adolescent refugees (40 males and 61 females) aged 13 to 24, who live in Seoul, Gyeonggi Province, and Busan. SPSS 25.0 and Mplus 5.12 were used to analyze data. Descriptive statistics and Pearson’s correlation coefficients were calculated and structural equation modeling (SEM) examined the mediating effect. The results of this study are as follows. First, a higher level of family support and friend support were associated with a higher level of internal locus of control. A higher level of internal locus of control was associated with a lower level of acculturative stress among North Korean adolescent refugees. Second, the level of internal locus of control mediated the relationship between friend support and acculturative stress. This study is meaningful in that it examines the specific paths affecting acculturative stress of North Korean adolescent by examining family and friend support, which are environmental factors, and internal locus of control, which is internal factor of individuals. The study results suggest that improving friend support as well as increasing the level of internal locus of control for North Korean adolescent refugees can be an effective way to prevent or intervene acculturative stress.