Borderline Personality Disorder (BPD) is widely considered the result of biological vulnerability and environmental adversity. Despite growing evidence for the role of several temperamental and environmental risk factors in the development of BPD, the unique contribution of each to the development of this disorder remains unclear. Furthermore, the extent to which these factors are associated with BPD among underserved and diverse populations is unknown. The current study examined the temperamental and environmental factors uniquely associated with BPD among a sample of 93 inner-city individuals receiving residential substance use treatment. Results indicate that BPD was associated with higher impulsivity and emotional instability/vulnerability, lower well-being, and several interpersonal manifestations of positive and negative temperament (i.e., greater alienation and lower achievement and social closeness). BPD was also associated with several forms of childhood maltreatment, including emotional and physical abuse and neglect. However, only emotional instability or vulnerability, impulsivity, and emotional abuse emerged as unique predictors of BPD status.