The aim of this study was to investigate the development of metacognitive strategy knowledge (MSK) during schooling at the upper secondary education level and to examine its relation with individual student characteristics. This longitudinal study with two measurement points analyzed a sample of students in grades 10 and 11 from 19 schools preparing students for university in Switzerland. The findings showed no development of MSK within a single year of school. Individual differences appeared in the level and the change of MSK over time. Female students as well as students with higher SES displayed higher MSK than male students and students with lower SES at the first measurement point. Furthermore, SES predicted changes in MSK over time. Between learning motivation and MSK as well as self-efficacy and MSK, high correlations were found at t1. Neither learning motivation nor self-efficacy had an effect on the change of MSK over time. The results show that there is still substantial potential for MSK development at the upper secondary education level. Implications for education and further studies are discussed.