In this study, the following questions were addressed in an undergraduate non-major biology course using a large lecture format: Is there a relationship between students' perceptions of their learning environment and course performance, and what roles do motivation and attitudes play in mediating that relationship? The purpose of this study was to test a path model describing the mediating effects of motivation and attitudes on learning environments and course performance. The study considered contemporary understanding of teaching and learning, as well as motivation and attitudes, in suggesting a direction for future reform efforts and to guide post-secondary science education instructors and leaders in the design of learning environments for undergraduate non-major biology courses. Among the classroom learning environment variables assessed in this study, personal relevance was the major contributor to predicting attitudes, motivation and course performance. Although the classroom learning environment had a very weak direct effect on course performance, there was a moderate total effect on self-efficacy and intrinsic goal orientation. The classroom learning environment also had a moderate total effect on attitudes toward biology. Attitudes toward biology had a moderate direct effect on self-efficacy. While attitudes toward biology was significantly correlated with course performance, the direct effect was extremely weak and was dropped from the model. However, attitudes toward biology had a moderate indirect effect on course performance due to the mediating effects of self-efficacy. Self-efficacy had a strong direct effect on course performance and therefore seemed to be particularly important. The model tested in this study explained 33% of the variance in course performance, 56% of the variance in self-efficacy, 24% of the variance in attitudes toward biology, and 18% of the variance in intrinsic goal orientation. To improve course performance, instructors should focus on building self-efficacy among their students and ensure that students find the course personally relevant.