A history of childhood sexual abuse (CSA) increases the risk of suicidal behavior and the lifetime number of suicide attempts in adults with BPD. Despite a strong association, specific variables mediating the relationship between CSA and adult suicidal behavior in BPD have not been identified. This study examined risk factors for suicidal behavior as potential mediators of the relationship between CSA and suicide attempts in 151 men and women with BPD. Diagnostic, clinical, and psychosocial risk factors, as well as CSA, and suicidal behaviors, were assessed by standardized interviews or self-rated measures. Psychotic and schizotypal symptoms, and poor social adjustment, were associated with both CSA and suicidal behavior, and partially mediated the relationship between CSA and attempter status. Psychotic and schizotypal symptoms in BPD define a vulnerability to cognitive and perceptual distortions under stress. They increase the likelihood of suicidal behavior in BPD, especially in the absence of mitigating social support. A theoretical model for suicidal behavior in BPD is presented which integrates direct, mediated, and moderated pathways between childhood sexual abuse and temperament, adolescent and adult risk factors, and suicidal behavior.