Despite historical concerns about the validity of the construct of borderline personality disorder (BPD) in adolescence, there is now general consensus that BPD in adolescence constitutes a valid and reliable diagnosis. Yet the development and refinement of measures to assess borderline traits in adolescents is in its infancy. Moreover, brief and easy-to-administer measures of borderline traits for use in large-scale studies do not exist. The aim of the current study was to evaluate the Borderline Personality Features Scale for Children (BPFSC; Crick, Murray-Close, & Woods, 2005) and develop a short version of the BPFSC through the use of item response theory (IRT) methods. BPFSC data from a community sample of 964 adolescents (mean age = 15.1 years, SD = .79; 55.9% female) were used to examine the factor structure of the BPFSC. The hypothesized 4-factor structure was not supported. The unidimensional IRT analysis showed instances of local dependence among item pairs and item responses that were not strongly related to the underlying construct. As a consequence, items were eliminated, creating a unidimensional 11-item brief BPFSC (the BPFSC-11). Next, evidence of construct validity of scores based on the shortened version was evaluated using a different sample of 371 inpatient adolescents. We demonstrated similar indices of construct validity as observed for the BPFSC total score with the BPFSC-11 scores and found evidence for good criterion validity. Use of the BPFSC-11 in clinical settings will reduce the burden on respondents without loss of information.