<p>While the association between metacognition and mathematical academic achievement has been well established, the underlying mechanisms linking them remain complex. Limited research has explored whether additional factors mediate this relationship. This study examined a sample of 965 students from 10 high schools in a province of China using a quantitative cross-sectional research design. The objective was to investigate the mediating effects of learning strategies and learning engagement in the relationship between mathematical metacognition and mathematical academic achievement. The findings revealed that: (1) mathematical metacognition showed significant associations with both learning strategies and cognitive and emotional engagement in learning; (2) emotional engagement fully mediated the relationship between mathematical metacognition and mathematical academic achievement; and (3) while mathematical metacognition did not directly relate to mathematical academic achievement through learning strategies, it was associated with students’ behavioural engagement by shaping their metacognitive strategies, ultimately relating to academic performance. These results underscore the importance of fostering mathematical metacognition in mathematics instruction, highlighting the role of emotions in students’ mathematical learning and reinforcing behavioural engagement through the integration of effective learning strategies to enhance mathematical academic achievement.</p>