The Diagnostic and Statistical Manual of Mental Disorders V (DSM V) characterizes Borderline Personality Disorder (BPD) as impairments across social functioning (e.g., an inadequately developed, unsteady self-image and constant conflict in relationships) and personality traits (e.g., negative affectivity, rejection sensitivity, impulsivity, and hostility). Because of these impairments, people with BPD frequently encounter serious problems such as emotion dysregulation and suicidality. Emotion dysregulation is defined as a lack of emotional comprehension, inability to cope with emotions in adaptive ways, and unacceptance of distress as part of goal accomplishment, and the lack of ability to pursue a goal in distress. Self-injurious behaviors (SIB), which captures both suicide and non-suicidal self-injury (NSSI), is also an issue to note for people diagnosed with BPD, because they are at higher risk for SIB. It is evident that emotional dysregulation and suicidality are clear disturbances to having a balanced, healthy life. The study pertains to investigate the relationship among emotion dysregulation, rejection sensitivity, and SIB across the patients’ treatment timeline. We first hypothesize a direct relationship between emotion dysregulation and SIB; prior research suggests that diagnosis of BPD will increase the likelihood of suffering from emotion dysregulation and SIB respectively. This is crucial, because it tests the theoretical model of the relationship between the two variables. Our second hypothesis aims to take a scope at how rejection sensitivity exerts a mediator effect on the relationship between emotion dysregulation and SIB among individuals diagnosed with BPD. We conjecture that higher rejection sensitivity will strengthen these two relationships. The study recruited 99 females diagnosed with BPD to assess their emotion dysregulation, rejection sensitivity, and SIB. Based on the analyses, we expect to provide an empirical support for the theoretical model and encourage future research to better promote health for individuals diagnosed with BPD.