Borderline personality disorder is a psychological disorder characterized by a pervasive pattern of instability in affect regulation, impulse control, interpersonal relationships, and self-image. Borderline personality disorder may be present in up to 6.4% of adult primary care visits, which is fourfold higher than in the general population. Borderline personality disorder is underdiagnosed and most patients who have it also have additional psychiatric conditions. Individuals with borderline personality disorder have an underlying vulnerability to emotional hyperarousal states and social and interpersonal stressors. Clinically these patients may have high health care utilization, health-sabotaging behaviors, chronic or vague somatic concerns, aggressive outbursts, high-risk sexual behaviors, and substance use. Obesity and binge-eating disorders are common comorbidities in those diagnosed with borderline personality disorder. There is an established correlation between borderline personality disorder and increased suicide risk. Structured interview assessments that are designed specifically for borderline personality disorder include the Revised Diagnostic Interview for Borderlines and the Structured Clinical Interview for the DSM-5 Alternative Model for Personality Disorders. As general guidelines for practice, family physicians should avoid excessive familiarity, schedule regular visits, set appropriate limits, and maintain awareness of personal feelings. Use of effective communication strategies such as motivational interviewing and problem-solving techniques can help navigate addressing problematic behaviors in patients who have borderline personality disorder. Multiple behavior treatments are useful, the most effective of which are dialectical behavior therapy and mentalization-based therapy. No medications have been approved by the U.S. Food and Drug Administration specifically for the treatment of borderline personality disorder.