The present study examined roles that perceived English fluency and sociocultural adaptation difficulty play in predicting self-efficacy beliefs for teaching in a sample of 119 international teaching assistants (ITAs) from East Asian countries of China, Japan, Korea and Taiwan. Results showed that a positive relationship between perceived English fluency and teaching self-efficacy was not apparent until the moderating influence of sociocultural adaptation difficulty was examined. More specifically, at high levels of adaptation difficulty, positive relations between English fluency and teaching self-efficacy were found; however, as sociocultural adaptation difficulty decreased, the effect of perceived fluency in English on efficacy decreased. Implications for ITA training as well as limitations of the study were discussed. (Contains 1 figure and 2 tables.)