11009 Background: YouTube is an open-access source of information. With more than 2.5 billion users, it can play a pivotal role in educating or misinforming cancer patients. ICI has changed the treatment paradigm for cancer over the past decade. There is scarce data to evaluate the quality of information on ICI uploaded on YouTube. We aim to assess the quality and engagement parameters of the 100 most viewed videos on YouTube focusing on ICI. Methods: A systematic search was conducted on YouTube using the search terms (“Immunotherapy AND Cancer”; “Immune Checkpoint Inhibitors AND Cancer”). The 100 most viewed English videos were selected. We utilized the already validated PEMAT1 and DISCERN2 tools to assess the quality of these videos on ICI. Additionally, we looked at the number of views, comments, and likes. Descriptive statistics and Pearson correlation tests were performed using R studio v2022.12.0-353. Results: The videos in our study had up to 42 million views (median views: 17,617). These videos were categorized by sources; academic (54%), media (31%), and industry (15%). The mean DISCERN score for the videos was 43.4. Only 22% videos were in the good or excellent category. Most videos (53%) discussed the benefits of ICI, whereas only 29% discussed the adverse effects of ICI. Shared decision-making was promoted by 34% of videos, and only 6.7% of videos summarized the information at the end, based on the DISCERN criteria. The medical terminologies were defined by 48.5% of videos, and 31% were broken into short sections with informative headers per PEMAT understandability criteria. There was no significant association between the video source and video engagement parameters, including likes, views, and comments. However, a trend towards an increased number of likes (r=-0.195, p=0.04) and comments (r=-0.213, p=0.03) was noticed with lower DISCERN scores (poor quality videos). Conclusions: The majority of YouTube videos are focused on the benefits of ICI. They are less likely to discuss the adverse effects or shared decision-making . In summary, YouTube videos contain biased information on ICI. Further efforts from academic institutions are needed to improve the quality and engagement of these videos. 1. Shoemaker SJ et al. The Patient Education Materials Assessment Tool (PEMAT) and User’s Guide; 2. Charnock D et al. DISCERN: an instrument for judging the quality of written consumer health information on treatment choices. J Epidemiol Community Health. 1999. Pearson correlation coefficient (r) between quality assessment scores and video variables. [Table: see text]