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The Level of Personality Functioning Scale–Self-Report (LPFS-SR) operationalizes Criterion A of the DSM-5 Alternative Model for Personality Disorders. The current study aimed 1) to examine the internal consistency of the Portuguese version of the LPFS-SR in a community sample and a clinical sample, 2) to compare non-clinical participants (N = 282, Mage = 48.01, SD = 10.87) with two samples of clinical participants, one composed of patients with a personality disorder diagnosis (PD sample, n = 40, Mage = 46.18, SD = 13.59) and the other of patients with other psychiatric diagnoses (OD sample, n = 148, Mage = 49.49, SD = 11.88), with respect to LPFS-SR dimensions and total score, 3) to examine the capacity of the LPFS-SR to discriminate between samples through the ROC curve analyses, and 4) to examine the factor structure of the Portuguese version of the LPFS-SR. The Portuguese version of the LPFS-SR revealed adequate internal consistency results, akin to the original data, in the community and clinical samples. The community sample differed significantly from both clinical samples in all the LPFS-SR dimensions and total score. The ROC curve analysis indicated an optimal cut-off for the total score of 272.00, corresponding to a sensitivity of 75% and a specificity of 89%, in the PD vs. community samples. The LPFS-SR total score discriminative capacity between the PD and OD samples was lower, albeit also significant (area-under-the-curve of .63; p = .027; 95% CI: .52-.74). The current study provided evidence of the LPFS-SR’s unidimensionality in both community and clinical samples. Although this study has limitations, its findings contribute to a deeper understanding of the LPFS-SR construct, as well as to its cross-cultural validation.