This paper reports a study of lower secondary mathematics classroom learning environments in Brunei Darussalam and their associations with students’ satisfaction with learning mathematics among a sample of 1,565 students from 81 classes in 15 government secondary schools. Students’ perceptions of the classroom learning environments were assessed with a version of the My Class Inventory (MCI) and a measure of student satisfaction also was included. Both measures had been modified for the Brunei context. The study revealed satisfactory reliability and validity for a refined three-scale version of the MCI assessing cohesiveness, difficulty and competition. Mean scores were generated from the data to provide a profile of what a typical classroom is like. Sex differences in classroom environment were explored using a one-way MANOVA with the set of MCI scales as the dependent variables. Overall, the study suggests that students’ perceived a positive learning environment in mathematics classes. Also the study supported earlier research suggesting that boys and girls hold different perceptions of the same classroom learning environments. Relationships between student satisfaction and classroom environment were investigated using simple and multiple correlation analyses. Associations between satisfaction and the learning environment were statistically significant both at student and class levels for most MCI scales.