Background: Sunscreen use is a popular sun protection method; however, application of sunscreen rarely meets the standards recommended for effectiveness. Access to information about how to effectively use sunscreen may play a role in proper sunscreen application. The internet is a common health information source; however, the quality of sunscreen-related content varies. Objective: The objective of this study was to examine information about sunscreen in YouTube videos by video source. Methods: In November 2017, the authors identified the 20 most popular YouTube videos (sorted by view count and relevance) for each of these 5 search terms: sunscreen cancer, sunscreen health, sunscreen information, sunscreen ingredients, and sunscreen natural. The inclusion criteria were English language and view count >1000 (N=111 unique videos). We double-coded videos for standard recommendations for sunscreen use (eg, apply 20 minutes before sun exposure), use of outdated terminology, and recommendation of complementary sun safety strategies. Results: The view counts ranged from 1100 to 671,142 (median 17,774, SD 109,651) and the average daily views ranged from 1 to 1448 (median 23, SD 234). End users (46/111, 41.4%) and health care providers (24/111, 21.6%) were the most common sources, and none of the most popular videos were produced by federal agencies or cancer-related nongovernmental organizations. Health care provider videos included marginally more recommendations than end user videos (mean 1.46, SD 1.96 vs mean 1.05, SD 1.20), but few (19/111, 17.1%) mentioned reapplication. The videos were generally positive toward sunscreen (82/111, 73.9%); however, some videos were negative (29/111, 26.1%), with warnings about the health risks of chemical sunscreens and their ingredients. Do-it-yourself sunscreen tutorials represented 19/111 (17.1%) of the sample. Conclusions: YouTube is a potential source for disseminating sun safety messages; however, the quality of its sunscreen content varies. Most of the videos in our study failed to include important sunscreen use recommendations. Clinicians should be prepared to address the information needs of patients by discussing effective, evidence-based sunscreen application and recommending a combined sun safety approach. [JMIR Dermatol 2020;3(1):e14411]