C ancer continues to be a leading cause of mortality and challenging public health problems worldwide. [1] In recent years, the complex interaction between cancer and nutrition has emerged as a prominent area of discussion, with a growing body of evidence highlighting the important role of dietary habits in the etiology, prevention, and treatment of various types of cancer. As researchers delve deeper into the complex molecular and metabolic mechanisms involved, understanding the nuanced relationship between dietary patterns, nutrient intake, and cancer risk has become a focal point in the multifaceted battle against this challenging disease. [2,3] Besides researchers, the public has a great interest in the relationship between cancer and nutrition. While healthy people are interested in this issue Objectives: YouTube, boasting an expansive number of users, is one of the primary sources of video-based educational content worldwide. The aim of this study was to assess the content of YouTube videos about cancer and nutrition. Methods: In this cross-sectional register-based study, popular videos on YouTube about the following keywords were evaluated; "cancer and nutrition", "nutrition in cancer patients", "chemotherapy nutrition", "nutrition in chemotherapy", and "nutrition after chemotherapy". and reliability of video content were measured using the Global Quality Score (GQS), Journal of the American Medical Association (JAMA), and the modified DISCERN (mDISCERN) tool. Results: A total of 136 videos were analyzed in the study. The median duration was 157 (30-2960) seconds and the median number of views was 1232.5 (9-1238570). Median viewing rate was 1.06 (0-732). Among the video publishers, television (TV) health programs were the most (n=42, 31%). Regarding the video category, the most (n=121, 89%) popular was informative videos for patients. In most of the videos, the narrators were non-oncology clinicians (n=41, 30%) and dietitians (n=40, 29%). Mean GQS, JAMA, mDISCERN scores were 2.25±0.95 (fair-poor quality), 1.65±1.89 (fairpoor quality), and 1.96±1.13 (poor quality), respectively. A positive correlation was found between the 3 scoring points (p<0.001 for all pairwise comparisons). There was a negative correlation between video age, duration and all of the quality scores. There was a significant difference between video quality scores according to video categories, publishers and narrators (p<0.001 for each). Conclusion: Patients and individuals who are curious about relationship between nutrition and cancer to access accurate information, individuals should be directed to the right resources. Making oncologists more visible in this field by receiving professional support and can help higher quality videos reach the public.