Adjustment disorder is one of the most prevalent mental disorders. However, there are almost no measures available for its assessment. We aimed to analyze the psychometric properties of a brief version of the International Classification of Diseases (ICD)-11 adjustment disorder scale (Adjustment Disorder New Module-8; ADNM-8) in a help-seeking sample. Data from 1,174 participants with an average age of 35 years who registered for the internet-based self-help adjustment disorder intervention were analyzed. Psychometric properties of the brief 8-item self-report (ADNM-8) scale measuring the 2 core adjustment disorder symptoms of preoccupation and failure to adapt were tested. Confirmatory factor analysis (CFA) was applied for the analysis of construct validity. CFA supported the 2-factor structure of ADNM-8. Further research is needed for validation of ADNM-8 in cross-cultural studies.