<p>Alcohol Use Disorder (AUD) has been associated with reproductive dysfunction, yet evidence regarding its long-term impact on infertility and whether this association differs by sex remains limited and methodologically inconsistent. To investigate the association between AUD and infertility in men and women using nationwide population-based data, and to formally evaluate whether this association differs by sex. We conducted a retrospective cohort study using Taiwan’s National Health Insurance Research Database. Individuals aged 15–49 years with newly diagnosed AUD were matched to non-AUD controls using propensity score matching within sex. Time-to-infertility was analyzed using Cox proportional hazards models. Sex differences were formally assessed using an AUD × sex interaction term and a four-group Cox model. Sensitivity analyses restricting both sexes to a common follow-up window were performed to evaluate the robustness of findings. AUD was associated with an increased risk of infertility in both men and women. In models including both sexes, the AUD × sex interaction term was statistically significant, indicating that the strength of the association differed by sex. These findings were consistent in sensitivity analyses using a unified follow-up period. Kaplan–Meier–based cumulative incidence curves showed higher unadjusted infertility incidence among individuals with AUD in both sexes. In this nationwide cohort study, AUD was associated with an elevated risk of infertility among individuals of reproductive age. Formal interaction analyses provided evidence that this association differs by sex. Although causal inference is limited by the observational nature of administrative data, these findings underscore the importance of considering sex-specific patterns when evaluating reproductive health outcomes in individuals with AUD.</p>