Therapies aimed at inhibiting tumour necrosis factor are currently successfully administered to an increasing number of patients with autoimmune diseases. Infliximab has been approved to induce and maintain remission in Crohn's disease and fistulizing Crohn's disease. We report a case of acute-onset flaccid paraplegia after the initiation of anti-tumour necrosis factor therapy (infliximab) for Crohn's disease. Neuroimaging findings revealed an extensive longitudinal myelopathy. Two months later, no abnormal signal intensity was observed in the spinal cord and after 4 months, the patient presented improvement of motor function. A possible correlation between anti-tumour necrosis factor therapy and acute myelitis is discussed. This case highlights that patients developing new neurological symptoms while on anti-tumour necrosis factor medication should be monitored closely.