The Flat Earth movement appears to have emerged from a combination of Biblical literalism (e.g., young Earth creationism, geocentrism) and conspiracy theorizing (e.g., belief that NASA faked the moon landings). Interviews with participants of the first International Flat Earth Conference in 2017 revealed that the majority of Flat Earthers have come to endorse Flat Earth ideas only within the last few years after watching videos on YouTube. However, the novelty of the movement means that there is a lack of literature on this group, including what exactly convinced these new Flat Earthers and how that conversion took place. Here, we provide evidence for a gradual process of conversion after multiple exposures to Flat Earth YouTube videos to which viewers were initially skeptical but report failing to adequately debunk. Furthermore, evidence is presented here regarding the crucial role YouTube played in their conversion process, suggesting the platform is potentially a strong avenue for changing beliefs. The narratives provided here also support much of the research on conversion, describing a gradual process of deep personal change, via the relatively new mechanism of social media, where one finds a new center of concern, interest, and behavior, as well as a different view of reality.