This study examined the construct validity of the McLean Screening Instrument for Borderline Personality Disorder (MSI-BPD) in a consecutive sample of adult psychiatric patients (n = 128) and a separate sample of undergraduate students (n = 289) in Singapore. Participants were administered the MSI-BPD and other measures assessing related symptoms of BPD. Patients were also administered a semistructured interview by interviewers blind to their MSI-BPD scores. Confirmatory factor analyses revealed a unique three-factor solution, consisting of affect dysregulation, self-disturbances, and behavioral and interpersonal dysregulation. In both samples, the MSI-BPD demonstrated good internal consistency and convergent validity. The measure also showed good discriminant validity and predictive accuracy (AUC = .82), with an optimal cut-off score of 7.5. Overall, the findings suggest that BPD is a valid and coherent clinical construct in Singapore, and point to the need to further clarify the presentation and etiology of BPD in this cultural context.