Functional neurological disorder (FND) is a complex condition involving an interaction of psychological, physiological, and social factors. Despite high utilization of medical services, people with FND often suffer from poor long-term health and psychosocial outcomes, and experience stigmatization and marginalization within the medical community. Health service psychologists are well positioned to help patients with FND through the lens of the biopsychosocial model of health. Psychologists can facilitate appropriate assessment and treatment, and advocate for the needs of patients diagnosed with FND within multidisciplinary teams. This article reviews best practices for assessment and treatment of individuals diagnosed with or suspected of having FND and presents some clinical and ethical challenges associated with this complex population.