Although there is much research related to students' achievement motivation, there is still very little research involving social relations at schools and the role of culture in these studies. This research analyses the relationship between teacher-student relations, peer relations, and achievement motivation, as well as whether collectivist culture moderates the relationship between teacher-student and peer relations on achievement motivation. Data was collected using a questionnaire adapted from the Student Teacher Relationship Scale (STRS), the Quality of Relationships Inventory (QRI) Scale, the Individualism-Collectivism Scale (ICS), and an achievement motivation scale. Data analysis used multiple regression analysis and the F. Hayes moderation test. An unexpected finding from this research is that the collectivist culture does not significantly moderate the relationship between teacher-student relations and achievement motivation; the collectivist culture does not significantly moderate the relationship between peer relations and achievement motivation, even though collectivist culture should have a strengthening effect on social relations of achievement motivation. The research results provide essential findings; namely, there is an indication of the transformation of cultural dimensions in the Z Generation who were participants in this research, so that the cultural dichotomy of individualism and collectivism becomes meaningless in the relationship among teacher-student relations and peer relations with achievement motivation. This research provides essential information on the development of science and future researchers to conduct a more comprehensive study of the dichotomy of the cultural dimensions of individualism and collectivism by involving two countries with different cultural backgrounds because cultural transformation is possible.