Background: Overdose deaths as a result of untreated opioid use disorder (OUD) pose a major public health concern across North America. Although slow-release oral morphine (SROM) is increasingly used as an alternative option for the treatment of OUD, research on its efficacy among individuals exposed to illicit fentanyl or those with previous unsuccessful attempts with other opioid agonist therapies (OATs) is limited and controversial. Case: We present a case of a 48-year-old male with severe OUD seeking treatment following a near-fatal fentanyl overdose. His previous treatment attempts with methadone and buprenorphine/naloxone-based OAT had been unsuccessful. As per local guidelines, he was started on SROM with subsequent cessation of opioid cravings and illicit drug use. Discussion: This case report describes a patient entering early remission for OUD when treated with SROM following unsuccessful past treatment attempts on first-line oral medications. Future studies should seek to evaluate SROM-based OAT as a potential second-line treatment alternative for OUD.