This study investigated the relationships of students' incremental beliefs of math ability to their achievement emotions, classroom engagement and math achievement. A sample of 273 secondary students in Singapore were administered measures of incremental beliefs of math ability, math enjoyment, pride, boredom and anxiety, as well as math classroom attention and disruption. In addition, students' end-of-year math achievement scores were collected from school records. The hypothesised mediation model was supported in structural equation modelling analysis. Incremental beliefs of math ability were associated positively with math enjoyment and pride, and negatively with math boredom and anxiety. Achievement emotions fully mediated the relationships of incremental beliefs of math ability to classroom engagement and math achievement. Incremental beliefs of math ability were associated positively with classroom attention through math enjoyment and pride, negatively with classroom disruption through math anxiety and positively with math achievement through the two outcome-related emotions, math pride and anxiety. The findings and implications are discussed in the academic context of Singapore.