Background: A new diagnostic concept of Adjustment Disorder (AjD) was proposed for inclusion in the International Classification of Diseases, 11th version (ICD-11). However, the symptom structure of AjD is poorly understood. The aim of the present study was to investigate the dimensionality of AjD as a stress-response syndrome. Methods: A general population sample of the Israeli population (N = 1003) completed the Adjustment Disorder – New Module 20 and the WHO-5 Wellbeing Scale. We compared seven alternative models of AjD using confirmatory factor analysis (CFA). A latent profile analysis (LPA) was performed to determine if subtypes of AjD were present. The performance of the unidimensional and multidimensional models of AjD were evaluated using regression analyses. Results: CFA results supported a unidimensional model of AjD. The LPA identified three quantitatively distinct classes (low, medium, and high) with no evidence of any subtypes of AjD. The criterion validity of AjD was superior when treated as unidimensional. AjD was associated with lower levels of psychological wellbeing (β = −.32, p < .001). Conclusions: Our results suggest that AjD is better conceptualised as a unidimensional construct. Future work should focus on a reduction of required symptoms in order to improve clinical utility and validity of the diagnosis.