Key Points Question Is receiving medical cannabis for a longer duration associated with reducing prescription opioid dosages among patients receiving long-term opioid therapy? Findings In this cohort study among 8165 patients with chronic pain receiving long-term opioid therapy, receiving medical cannabis for a longer duration was associated with prescription opioid dosage reduction. Higher opioid dosages were associated with larger reductions. Meaning These findings contribute evidence toward potential clinical benefits of medical cannabis in reducing prescription opioid intake, which may decrease patients’ risk of opioid overdose. Abstract Importance Patients with chronic pain often receive long-term opioid therapy (LOT), which places them at risk of opioid use disorder and overdose....