In this study, we measured students' perceptions of mathematics classroom learning environment and investigated their associations with students' achievement. The Mathematics-Related Constructivist-Oriented Classroom Learning Environment Survey (MCOLES) was developed with seven dimensions and 56 items, using theories surrounding classroom learning environment. For a sample of 423 grade 10 students from five schools in India, we validated the MCOLES by exploratory factor analysis and then by confirmatory factor analysis, which suggested the exclusion of 11 items and yielded an 11-factor solution. For achievement on a topic taught, mainly medium correlations emerged with the learning environment factors, suggesting practical implications for classroom teaching. This study is methodologically significant in proposing and validating the new MCOLES for measuring classroom learning environments in secondary-school mathematics.