Abstract: We report a case of intractable pain in a patient with amyotrophic lateral sclerosis (ALS) that was successfully managed by administering a fentanyl transdermal patch. Case: A 75-year-old man was diagnosed with ALS in 2013 after he became aware of difficulty in walking and systemic pain since 2010. In 2019, he underwent gastrostomy and tracheostomy, and intractable generalized pain necessitated the administration of morphine hydrochloride six times a day; however, it could not provide adequate pain relief. Later, morphine was replaced with a fentanyl patch under a very strict safe-monitored setting and the pain became bearable. Discussion: Although high-level evidence is lacking, pain experts have reported the effectiveness of morphine for intractable pain in patients with ALS. Frequent short-acting morphine dosing is often burdensome due to the complexity of its administration and it also causes end-of-dose pain. A fentanyl patch may possibly improve these drawbacks.