This study investigated middle school students' engagement in science in relation to students' perceptions of the classroom learning environment (teacher support, student cohesiveness, and equity) and motivation (self-efficacy beliefs and achievement goals). The participants were 315 Turkish sixth and seventh grade students. Four hierarchical multiple regression analyses were conducted on the dependent variables of cognitive, behavioral, emotional, and agentic engagement. The results indicated that engagement components were positively predicted by most of the perceived learning environment variables, while motivational factors had some differential predictive effects on engagement components. The predictor variables explained 26, 28, 33, and 30% of the variance in the cognitive, behavioral, emotional, and agentic engagement components, respectively.