Wilson's disease is characterised by deposition of copper in various tissues of the body, most markedly in the liver and the brain. Cerebral involvement, evident as neuropsychiatric symptoms, may be the presenting form of the illness in up to 50% of the adults. When patients present initially with psychiatric manifestations, the correct diagnosis is frequently missed. This case report describes an adult in his late 20's who presented with symptoms of major depressive disorder, but failed to respond to standard antidepressant treatment. He instead developed neurologic symptoms like tremor, gait disturbance, weakness of grip and clumsiness. Diagnosed as a case of conversion disorder, brain MRI showed abnormalities in the basal ganglia. Further investigations revealed that he had adult-onset Wilson's disease. Because of rarity, adult Wilson's disease patients with initial psychiatric presentations are frequently misdiagnosed and definitive treatment with chelating agents is not offered with continual organ damage from copper accumulation.