Background <p>The relationship between teacher support and students’ mathematics achievement has been extensively studied. However, its underlying mechanism remains unclear.</p> Methods <p>This study aimed to examine the associations between teacher support and mathematics achievement among high school students, and to test the potential mediating roles of mathematics anxiety and learning engagement in these associations. Participants included 1,340 high school students (<i>M</i>_<i>age</i> = 16.71&#xa0;years), and all participants completed questionnaires measuring teacher support, math anxiety and learning engagement, as well as three standardized mathematics achievement tests. The data analysis in this study was performed using the structural equation model (SEM) in SPSS 25.0 and Mplus 8.3.</p> Results <p>The results revealed that: (1)teacher support was positively correlated with mathematics achievement; (2)mathematics anxiety mediated the relationship between teacher support and mathematics achievement; (3)learning engagement mediated the relationship between teacher support and mathematics achievement; (4)mathematics anxiety and learning engagement jointly played a chain mediating role in the relationship between teacher support and mathematics achievement.</p> Conclusion <p>These findings highlight the significant associations between perceived teacher support and mathematics achievement among high school students, mediated through cognitive and behavioral mechanisms, thus providing preliminary correlational evidence that may inform future longitudinal and experimental research on educational practices.</p>