Borderline Personality Disorder (BPD) is a DSM-5 Cluster B mental health condition. One of the lesser understood mental health conditions, BPD is marked by a multi-symptom profile such as high levels of emotional dysregulation, distorted self-image, volatile and unstable relationships, emotional instability, and higher levels of suicidality. Symptoms are often intense and enduring, causing significant chaos and stress in an individual’s life as well as those closest to them. Because there is a significant overlap of symptomology and diagnosis with other psychiatric disorders, BPD was at one time a contested diagnosis, thus research and treatment options remained limited. Currently, BPD is one of the more widely researched conditions, which has informed evidenced-based treatment, however, individuals carrying the diagnosis report difficulty accessing treatment and difficulty feeling understood by mental healthcare providers. The development of BPD remains unclear, although consistent with other mental health conditions there is a genetic constituent, and with BPD in particular a history of trauma. This research manual will explore current evidence-based practices and assessment methods to inform best practices when working with BPD.