Pernicious anaemia can present with psychiatric symptoms before haematological or neurological manifestations appear. We describe a young woman who presented with insidious onset catatonia without evidence of psychosis or depression. Blood count and mean cell volume were normal and neurological findings were equivocal. Low B12 levels and intrinsic factor antibodies were found only by chance when they were included in a battery of further investigations. B12 replacement was followed by prompt improvement. This case provides an argument for wider screening for B12 deficiency in certain individuals with psychiatric disorders.