Introduction: Access cavity preparation is a crucial step in root canal treatment but is one of the most complex procedures in the curriculum to learn, with students often reporting spatial orientation difficulties during drilling. The present study aimed to evaluate the influence of spatial abilities on the preparation of endodontic access cavities among third-year dental students. Materials and Methods: Students from Lyon dental faculty participated voluntarily. The mental rotation test (MRT) evaluated spatial ability. Students prepared access cavities on 3D-printed mandibular molars, subsequently scanned and assessed against eight evaluation points, including morphology, canal access, floor preservation and convergence angle. Principal component analysis (PCA) assessed dataset variations. Results: A total of 43 volunteers participated. PCA revealed two principal components accounting for 80.8% of variations: the first PC primarily consisted of MRT score (64.3%) and morphology (14.1%); the second comprised operative time (46.1%) and morphology (18.0%). There were significant differences in morphology based on MRT scores, but no correlation was found between other parameters. Discussion: Lower MRT scores were associated with larger cavity preparations, raising questions about potential curriculum adaptations to enhance spatial reasoning. The operative time was not correlated with higher MRT scores but did contribute to variations in cavity morphology. Conclusion: Spatial abilities have a substantial impact on the quality of endodontic access cavity preparations; further studies should evaluate if the incorporation of 3D atlas exercises could be beneficial.