Despite the huge popularity of YouTube, there has been little research into the factors affecting educational applications of this social medium. This study attempts to predict and compare factors influencing YouTube acceptance among university students and educators in two very different cultures, Japan and the USA, applying the Unified Theory of Acceptance and Use of Technology (UTAUT). Five hundred and sixty-nine students and 56 educators from Japanese and American universities were surveyed to assess the influence of UTAUT-related factors on YouTube acceptance in these two countries. The paper reports on the findings, proposes further studies and offers some suggestions for the use of YouTube in education.