Background: Socialization practices support undergraduates' transitional processes when beginning their academic careers and afterwards. Anyhow, the absence of specific socialization measures for academic contexts does not allow Universities to assess it. Aims: The present study aimed to contribute to the socialization literature by proposing a reliable measure (USQ, Undergraduate Socialization Questionnaire) specific for the academic context, that is, reflecting the same construct at different developmental stages. Method and samples: Based on an organizational socialization scale (NSQ; Haueter al., 2003, "Journal of Vocational Behavior," 63, 20), we examined in Study One the USQ's three-factor structure (task, group, organization) (n. 451 undergraduates) and, in Study Two, we tested the construct invariance across time, comparing undergraduates' developmental changes through a two-wave longitudinal design (n.185 undergraduates attending their first and their second year). Results: Findings supported both the USQ's dimensionality and measurement invariance, thus ensuring that the same underlying construct is being assessed, and its concurrent and predictive validity. Conclusions: Overall, results showed that USQ is a reliable instrument useful to monitor the effectiveness of undergraduates' adjustment process, also allowing comparison between specific groups of students or longitudinal comparison to evaluate their career development or the effectiveness of policies targeted to reduce the risk of marginalization and dropout.