We seek to evaluate whether Internet Gaming Disorder (IGD) among university students in Mexico during their first year at university predicts a long list of mental disorders a year later, controlling for baseline mental health disorders as well as demographics. This is a prospective cohort study with a one-year follow-up period conducted during the 2018-2019 academic year and followed up during the 2019-2020 academic year at six Mexican universities. Participants were first-year university students (n = 1741) who reported symptoms compatible with an IGD diagnosis at entry (baseline). Outcomes are seven mental disorders (mania, hypomania, and major depressive episodes; generalized anxiety disorder and panic disorder; alcohol use disorder and drug use disorder), and three groups of mental disorders (mood, anxiety, and substance use disorders) at the end of the one-year follow-up. Fully adjusted models, that included baseline controls for groups of mental disorders, rendered all associations null. The association between baseline IGD and all disorders and groups of disorders at follow-up was close to one, suggesting a lack of longitudinal impact of IGD on mental disorders. Conflicting results from available longitudinal studies on the role of IGD in the development of mental disorders warrant further research.