Introduction: There is a growing body of literature supporting the efficacy of cannabis-based medicinal products (CBMPs). Despite an increase in prescribing globally, there is a paucity of high-quality clinical data on the efficacy of CBMPs for many conditions. This study aims to detail the changes in health-related quality of life (HRQoL) and associated clinical safety in patients prescribed CBMPs for any clinical indication from the UK Medical Cannabis Registry (UKMCR). Methods: An uncontrolled prospective case series of the UKMCR was analyzed. Primary outcomes included change from baseline in patient-reported outcome measures collected across all patients (the Generalized Anxiety Disorder Scale [GAD-7], EQ-5D-5L, and Sleep Quality Scale [SQS]) at 1, 3, and 6 months. Secondary outcomes included the self-reported incidence and severity of adverse events. Statistical significance was defined as p<0.050. Results: Three hundred twelve patients were included in the final analysis, with a mean age of 44.8. The most common primary diagnoses were chronic pain of undefined etiology (n=102, 32.7%), neuropathic pain (n=43, 13.8%), and fibromyalgia (n=31, 9.9%). Before enrolment, 112 (35.9%) patients consumed cannabis daily. The median cannabidiol and (-)-trans-Δ9-tetrahydrocannabinol doses prescribed at baseline were 20.0 mg (0.0-510.0 mg) and 3.0 mg (0.0-660.0 mg), respectively. Statistically significant improvements were observed in GAD-7, EQ-5D-5L Index, EQ-5D Visual Analog Scale and SQS scores at 1, 3, and 6 months (p<0.050). There were 94 (30.1%) reported adverse events, of which nausea (n=12, 3.8%), dry mouth (n=10, 3.2%), dizziness (n=7, 2.2%), and somnolence (n=7, 2.2%) were the most common. Conclusion: This study demonstrated CBMP treatment to be associated with a relatively low incidence of severe adverse events in the medium-term. Positive changes following treatment were observed in general, as well as anxiety and sleep-specific, HRQoL outcomes. Randomized controlled trials are still awaited to assess causation; however, real-world evidence can help inform current clinical practice, future trials, and is an important component of pharmacovigilance.