ENBackground: Although there is increasing knowledge about adjustment disorder (AjD) based on the new diagnostic criteria of the International Classification of Diseases (ICD-11), less is known on AjD in adolescents. This study aimed to examine the prevalence of AjD and its risk factors in Japanese and Lithuanian adolescents. Methods: The cross-sectional study sample comprised 1745 adolescents from Japan (n = 913) and Lithuania (n = 832). AjD was assessed using the Adjustment Disorder New Module-8 (ADNM-8). We compared the prevalence of AjD in Japanese and Lithuanian adolescents. Using multinominal logistic regression analysis, we examined the effects of age, gender, socioeconomic status, and cumulative stressors as societal and cultural factors, resilience as an intrapersonal factor, and loneliness and perceived support as interpersonal factors on adolescent AjD. Results: The prevalence of probable AjD was 11.7% in Lithuanian adolescents and 6.9% in Japanese adolescents. Gender, socioeconomic status, cumulative stressors, resilience, loneliness, and perceived positive social support were each significantly associated with AjD risk. Conclusions: This cross-cultural comparative study revealed characteristics of the stressors and prevalence of AjD among Japanese and Lithuanian adolescents. In terms of the socio-interpersonal framework model for the stress–response syndrome, sociocultural, intrapersonal, and interpersonal factors were found to be risk factors associated with AjD in adolescents. Keywords: adjustment disorder; adolescents; cross-cultural; socio-interpersonal model. [From the publication]