Depression is rare in early childhood and unusual in autism in this age group. We describe a female child aged 6 years with autism who presented with regression of developmental skills previously gained. Her sleep and appetite were poor, her affect was sad, and she had morbid speech content. She responded to treatment with antidepressant medication. When this clinical picture occurs in adults it is called depressive pseudodementia; paediatric neurologists and neuropsychiatrists need to be aware of it in children.