Aim: No measure has formally been developed to assess the published ICD-11 model of Personality Disorder (PD) severity. We therefore set out to develop and evaluate the 14-item Personality Disorder Severity ICD-11 (PDS-ICD-11) scale. Method: A representative U.S. community sample (N = 428; 50.9% women) and a New Zealand mental health sample (N = 87; 61.5% women) completed the PDS-ICD-11 scale along with a series of established PD and impairment measures. Results: Item response theory supported the unidimensionality of PDS-ICD-11 (median item loading of 0.68) and indicated that a PDS-ICD-11 score of 17.5 may serve as a benchmark for pronounced dysfunction. Correlation and regression analyses supported both criterion validity and incremental validity in predicting impairment and PD symptoms. The PDS-ICD-11 was particularly associated with measures of Level of Personality Functioning Scale (LPFS), Global PD severity, and Borderline PD symptom score. A comparison between clinical individuals diagnosed with an ICD-11 PD vs. no PD supported diagnostic validity. Conclusion: This initial construction study suggests that the PDS-ICD-11 constitutes a promising instrument that provides a quick impression of the severity of personality dysfunction according to the official ICD-11 PD guidelines. Clearly, more research is needed to corroborate its validity and utility. The PDS-ICD-11 scale is provided as online supporting information.