The Guilllain-Barré syndrome (GBS) is an acute predominantly demyelinating polyneuropathy. In many cases GBS is preceding by infection, immunization, surgery or trauma. Although there are a few reports of GBS after head trauma, there is no report of this syndrome after brachial plexus injury. We report on a 51 years-old man who presented GBS fifteen days after a brachial plexus trauma. The polineuropathy resolved completely in a few weeks. We believe that GBS was triggered by the trauma that evoked an immune mediated disorder producing inflammation and demyelination of the peripheral nerves.