Background: The prediction and explanation of academic performance and the investigation of the factors relating to the academic success and persistence of students are topics of utmost importance in higher education. Aims: The main aim of the present study is to develop and test a conceptual framework in a university context, where the effects of achievement goals, self-efficacy and class size on academic performance are hypothesized to be direct and indirect through study strategies. Sample: Participants were 553 students of different faculties from a university in Spain. Method: Pre-existing scales were used to develop the questionnaire. Questionnaires were group-administered in 21 classes during the first 2 weeks of May (i.e. about 1 month before the final examination). At the end of the academic year, students' grades were obtained from professors of each course. Results: Data were analysed through structural equation modelling. The results of the structural model provided support for most of the hypothesized relationships. Achievement goals and self-efficacy had no direct effects on performance, but results from the model comparison suggested that a mediational model provided a better fit to the data. Conclusions: Our study provides support for the key mediational role of study strategies in the effect of achievement goals and self-efficacy on academic performance. Self-efficacy seems to have the strongest indirect effect on performance. Mastery goals play a key role increasing deep processing and effort, and in turn affecting performance. Academic performance tends to diminish with increasing class size.