The Borderline Personality Features Scale for Children (BPFS-C) was recently shortened using item response theory to an 11-item version that is optimal for use in epidemiological studies and repeated assessment over time. Only 1 study has examined invariance of the BPFS-C-11 items across gender and no study has done so over time. The present study employed a longitudinal design to address this gap by evaluating measurement invariance across gender and over time during the transition into adulthood in a diverse community-based sample of 755 adolescents (56% female). Results indicated measurement variance for items measuring personal relationships and impulsivity/recklessness, with females having a greater probability of endorsing items regarding relationship instability and males more likely to endorse impulsivity, despite an equal position on the latent trait. Overall, there was partial measurement invariance of a single dimension of borderline features between males and females and full longitudinal invariance of this factor through the transition into young adulthood. The current findings provide empirical evidence supporting the reliability of BPFS-C-11 scores as a measure of borderline pathology (BP) during late adolescence and early adulthood.