Global concern surrounds students' mathematics learning, development, and achievement. Scholarly discussions have explored various factors influencing students' mathematics performance. However, more information is needed to understand the impact of mathematics teaching styles on student outcomes in developing contexts like Nepal. This study examines the moderators of mathematics teaching styles and their influence on students' performance. To achieve this, the Teachers' Teaching Style Questionnaire (TTSQ) collected quantitative data from 469 grade nine students across 14 high schools in Kathmandu, Lalitpur, and Bhaktapur districts of Nepal. Confirmatory factor analysis, path analysis, and moderation analysis were performed to examine the effects of teaching styles on student achievement in mathematics. Key findings indicate that teaching styles, such as consideration and openness, are not significant predictors of student achievement, but rigid teaching styles can predict student achievement in mathematics. However, impact of the rigid teaching style was negative on student achievement. School type influenced the relationship between performance and considerate teaching, favoring private schools. School location influenced the relationship between considerate teaching and student performance in mathematics, favoring rural schools. Likewise, urban schools had a negative effect on the relationship between teacher openness and student performance, but rural schools had a positive effect on their relationship. Furthermore, low and high-ability students moderated the relationship between considerate teaching and student achievement, with the negative effect of low ability on considerate teaching and student performance and the positive influence of high ability on considerate teaching and student achievement. Student ability influenced the relationship between teacher openness and student performance, with a negative moderations of low and moderate ability students. The study concludes by emphasizing the importance of teacher training in teaching styles for high schools in Nepal and similar contexts.