The purpose of the current study was to examine the criterion validity of the Borderline Personality Features Scale for Children (BPFS-C) by assessing the performance of the self-report and a newly developed parent report version of the measure (BPFS-P) in detecting a borderline personality disorder (BPD) diagnosis in adolescent inpatients. This study also examined parent-child agreement and the internal consistency of the BPFS subscales. An inpatient sample of adolescents (n = 51) ranging from ages 12-18 completed the BPFS and were administered the Child Interview for DSM-IV Borderline Personality Disorder (CI-BPD) by trained clinical research staff. ROC analyses revealed that the BPFS-C has high accuracy (AUC = .931; Se = .856; Sp = .840) in discriminating adolescents with a diagnosis of BPD, as measured by the CI-BPD, while the BPFS-P has moderate accuracy (AUC = .795; Se = .733; Sp = .720). Parent-child agreement on total scores was significant (r = .687; p < .005). Cronbach's alphas suggested internal consistency for the four subscales of the BPFS. These findings support the criterion validity of this measure, particularly the self-report version, in adolescent inpatient settings.