Colonoscopy is the primary method for diagnosing colonic diseases and detecting precancerous lesions, thereby playing a crucial role in the prevention of colorectal cancer. However, the scientific quality and reliability of these videos require systematic assessment. In addition, the scientific quality of Turkish colonoscopy videos on YouTube remains unexplored. This study used internationally recognized scoring systems to assess the scientific quality of Turkish colonoscopy-related videos on YouTube. This cross-sectional study analyzed 156 Turkish-language YouTube videos on colonoscopy, with the inclusion criteria requiring a video duration between 30 seconds and 60 minutes. The main outcomes were video quality and information accuracy, which were measured using the Journal of the American Medical Association (JAMA), modified DISCERN (mDISCERN) score, colonoscopy data quality (C-DQS), and Global Quality Score (GQS) tools. The study included 156 videos that fulfilled the inclusion criteria. According to the mDISCERN score, 24.4%, 59%, and 16.7% of the videos were of poor, fair, and good quality, respectively. Only 12.8% of the videos met the JAMA's quality criteria. The overall average score for each video source was low, with an average C-DQS score of 7.1/40. The JAMA, C-DQS, GQS, and mDISCERN scores for the videos designed to educate healthcare professionals were higher than those for videos designed for patient information or general culture/patient experience (P < .001 for each). Significant correlations were found between the JAMA score, mDISCERN score, GQS, and C-DQS (P < .001). Four independent quality assessment scales were used to evaluate Turkish-language YouTube videos on colonoscopy, with the results indicating suboptimal to moderate information quality. Online platforms, including YouTube, should implement strict quality control measures to ensure the accuracy of health-related videos.