Academic performance (GPA) is a fundamental factor in student success in college. Therefore, knowing the factors that influence it is important for universities. The objective of this research is to identify the determinants of university student academic performance during the first 3 years of its trajectory. The conclusions are based on data describing characteristics and behaviour of students who successfully completed three consecutive years of study in 10 public and private universities in Chile. The student participants were drawn from a selected list of all non-repeating students who entered the university in 2016 or in 2017. Data were collected from admission files and using a self-administered 39-item questionnaire. The questionnaire was applied during the first semester of 2021. Data were analysed using multilevel linear regression to control for similarities between students in the same programme. The findings show that both pre and post-enrolment variables affect performance. However, the influence of each factor varies according to the year of study. While, over the years, the importance of gender and secondary school grades increases and remains the same, respectively, selection tests are particularly important in the first year. In turn, variables associated with university experience, such as the relationship with professors or the occurrence of disruptive situations, affect performance from the first to the third year.