Although a vast body of studies regarding the variables related to students' achievement exists, only a handful has investigated how these variables combine and interact together. Such an investigation might make it possible to more accurately illustrate the heterogeneity of students enrolling in university and assess the impact of this diversity on academic achievement. The current study focused on the person-centered approach and investigated the possibility of determining significant subgroups of freshmen in the very first week of the academic year in the Belgian educational context. Using k-mean clustering, 2178 freshmen were classified according to their past performance, socioeconomic status, study choice process, and academic self-efficacy beliefs at the beginning of the first year at university. Analyses of variance were also conducted to analyze the relationship between these student clusters and academic achievement outcomes. Six distinct profiles of students were identified representing different combinations of achievement predictors. Results revealed different odds of success among these profiles. The implications of our approach to the understanding of the heterogeneity of freshmen and the first-year achievement process are discussed.