Behavioral variant frontotemporal dementia, the most common form of frontotemporal dementia, is characterized by executive dysfunction and changes in personality and behavior, sometimes with associated psychiatric disorders. We report a man who suddenly developed a gambling disorder when he was 55 years old. A year later he developed personality changes of agitation, euphoria, and disinhibition, along with binge eating and dysthymia. He did not improve on paroxetine 40 mg/day. Two years after the onset of his symptoms, he came to our clinic for evaluation. Neuropsychological testing showed deficits in cognitive control, planning, and attention. Brain magnetic resonance imaging and 18F-fluorodeoxyglucose positron emission tomography scans showed predominant frontal and temporal alterations, worse in the right hemisphere than the left. Cerebrospinal fluid analysis was not compatible with Alzheimer disease. On the basis of current criteria, we gave him a diagnosis of probable behavioral variant frontotemporal dementia presenting with a psychiatric symptom. Our findings in this unusual patient confirm the importance of close clinical monitoring in people who have a psychiatric disorder with atypical features, because the condition may mask an underlying neurodegenerative disease.