We examined age differences in self-perceptions of five dimensions of mastery motivation and also of competence in American, Chinese, and Hungarian children and teens. Participants included 200 Americans, 1,465 Chinese, and 8,175 Hungarians from 7 to 19 years of age. The Dimensions of Mastery Questionnaire provides comparable data across these different cultures as indicated by very similar factor structures and reasonably good internal consistency reliabilities for the scales. Across all three cultures, there was the expected decline from primary to secondary school in total persistence and the four instrumental mastery motivation scales, except for social persistence with adults in the American sample. Mastery pleasure did not decline in the American and Chinese samples but declined in the Hungarian sample. Self-perceived competence did not decline significantly in the American sample or in the Hungarian sample from age 11 to 17; however, competence self-ratings declined in the Chinese sample. The three cultures were compared at 11 and 16. Although there were some significant differences, small effect sizes indicated that the level of motivation was similar for each culture at each age. The other literature provides clues about why the declines occur in all three cultures and why there are some differences among cultures.