Patients with cancer sometimes are admitted to the emergency room due to severe pain. Despite the fact that morphine's hydrophilicity can delay its peak effects after intravenous administration up to 30 minutes, it is still the most commonly used opioid during cancer pain emergencies. Fentanyl is a synthetic, lipophilic opioid, more potent than morphine, and achieves peak effects after intravenous administration in 5 minutes. According to our observations, intravenous fentanyl could be safely used in the emergency room to treat patients who need fast titration of an opioid to control their pain. In our study, fentanyl was employed in a four-step protocol to treat patients admitted to our palliative care emergency room due to severe pain, regardless of the previous use of morphine at home. Titration with intravenous fentanyl was successfully employed in 18/18 (100%) of patients, with an average time for pain control at about 11 minutes, and without relevant adverse effects. We conclude that intravenous fentanyl could be safely used for severe cancer pain when rapid titration is being considered.