Guillain-Barr & eacute; Syndrome (GBS) is an acute inflammatory polyradiculoneuropathy that affects the peripheral nervous system, predominantly impairing motor function. Pain, both somatic and neuropathic, reported in 89% of cases and is refractory to first-line analgesics in most of these. We present the case of a 75-year-old woman with an acute presentation of are flexic flaccid tetraparesis compatible with GBS. She received treatment with intravenous immunoglobulin (IVIg), which improved the motor component, but she experienced pain refractory to nonsteroidal anti-inflammatory drugs and pregabalin, as well as persistent urinary retention with unsuccessful attempts to remove the urinary catheter. Transdermal fentanyl was administered with good response and tolerance, in addition to tamsulosin and intermittent catheterization, resulting in the successful removal of the catheter after six weeks. Based on this case, individualized evaluation of pain and urinary retention in CBS is suggested, considering the use of transdermal opioids and non-invasive bladder emptying measures, respectively.