YouTube has been influential in propagating Flat Earth Ideology, but not everyone is equally susceptible to the effects of watching these videos. In an experiment with a participant pool restricted to regular YouTube users, we found that lower science intelligence and higher conspiracy mentality increase individuals’ susceptibility to flat Earth arguments on YouTube. In fact, these two dispositional variables interact: whereas people with lower conspiracy mentality do not find the arguments compelling at any level of science intelligence, among those with higher conspiracy mentality, perception of argument strength decreases as science intelligence increases. Moreover, perceptions of argument strength varied on the thrust of the clip’s argument (science-, conspiracy-, or religious-based), with the religious appeal being perceived as weaker and inspiring more counterarguing than the science clip. We discuss implications for both the knowledge deficit hypothesis and for the differential susceptibility to media effects model.