The concept of growth mindset has been touted as a promising tool to empower learning, but mixed effects emerge. Growth mindset advocates are calling for more attention to the heterogeneity of growth mindset, namely, the interference of other factors at individual or contextual levels (e.g., teacher variables) with the relationship between growth mindset and learning achievements. To seek more evidence for this assumption, the current study explored the role of students' perception of their teacher support in predicting the quantity of growth mindset and the magnitude of the association between growth mindset and learning achievement in reading. We drew on the Programme for International Student Assessment (PISA) 2018 data from 507,354 students from 74 countries/territories. We analyzed the data with multilevel structural equation modeling with latent interaction. Our findings showed that perceived teacher support did not significantly predict the quantity of growth mindset. Besides, perceived teacher support positively moderated the relationship between growth mindset and reading achievement. Specifically, when teacher support was deficient, the relationship between growth mindset and reading achievement was negative; when teacher support continually increased, the relationship between growth mindset and reading achievement gradually switched to positive. These results indicated that teacher support plays a game-changing role in the relationship between growth mindset and reading achievement, therefore highlighting its significance in revealing the heterogeneous effect of a growth mindset effect on learning achievements.