307 Background: Immune checkpoint inhibitors (ICIs) are first-line therapy for several cancers and have novel toxicities that are important for patients to understand. We developed UPLIFT (Understanding and Preparing for Life on Immunotherapy), an educational intervention for adults with advanced cancer initiating ICIs. We aimed to test the feasibility, acceptability, and preliminary efficacy of UPLIFT on immunotherapy knowledge and anxiety. Methods: We conducted a pilot randomized controlled trial (NCT04670445) of 130 adults (age ≥18 years) who were initiating an ICI for advanced (stage IV or unresectable stage III) cancer to compare UPLIFT, an educational video and question prompt list (QPL) intervention to promote discussion about risks and benefits of ICIs, versus usual care. Participants were randomized 1:1 to receive UPLIFT prior to ICI initiation (intervention) or after 6 weeks (control). Participants were administered surveys at enrollment (baseline), within 72 hours after their oncology visit on ICI initiation date (72h), and 6 weeks post-ICI initiation. The primary outcome was feasibility, defined as 70% enrollment among approached patients and 80% having watched the video and reviewed the QPL. We also assessed acceptability of UPLIFT (3-item survey), immunotherapy knowledge (8-item survey, scored as % correct), and anxiety (State subscale of State and Trait Anxiety Index-Short Form). We used ANCOVA models, adjusted for age and baseline scores, to analyze knowledge and anxiety outcomes. Results: We approached 178 eligible patients and enrolled 130 patients in the trial (73%). 66 patients were randomized to receive UPLIFT and 65 to waitlist control. Patients (38% female, mean age=67 years) had diagnoses of advanced melanoma (40%), lung cancer (26%), renal cell carcinoma (8%), hepatocellular carcinoma (8%), or other cancers (18%). All 66 (100%) patients assigned to UPLIFT watched the video and received the QPL; 47% reported using the QPL during their oncology visit. 94% of patients in the intervention group reported they were “somewhat” or “very comfortable” with the video and QPL. Patients assigned to UPLIFT had improvements in immunotherapy knowledge from baseline to 72h relative to control patients (difference between adjusted mean % correct: 9% [95% CI: 3% to 16%]). The change in anxiety from baseline to 72h was not significantly different between the groups (0.6, 95% CI: -2.6 to 3.8). There were no differences between groups in the change in knowledge or anxiety scores from baseline to 6 weeks. Conclusions: A novel intervention to educate patients about the risks and benefits of ICIs not only was feasible to deliver and acceptable, but also improved immunotherapy knowledge relative to usual care among patients with advanced cancer, without increasing anxiety. A future study to evaluate the efficacy of UPLIFT is warranted. Clinical trial information: NCT04670445 .