The aim of this study was to evaluate the association between advanced paternal age (APA) and intrauterine insemination (IUI) outcomes. This retrospective cohort study included 861 IUI cycles in couples in which the female partner was ≤ 35 years. Patients were stratified according to paternal age into a control group (< 40 years) and a study group (≥ 40 years). The study group was further subdivided into two categories of APA: men aged 40–44 years and ≥ 45 years. Primary outcomes were clinical pregnancy rate (CPR), miscarriage rate (MR), and live-birth rate (LBR). No significant differences were observed between the control and the study groups in CPR (17.9% vs. 16.9%), MR (7.5% vs. 15.7%), or LBR (15.2% vs. 12.8%) (all p > 0.05). A subgroup analysis showed no differences between controls and men aged 40–44 years. In contrast, in men aged ≥ 45 years, MR was significantly higher (44.4% vs. 7.5%, p < 0.05) and LBR was significantly lower (6.6% vs. 15.2%, p < 0.05). Paternal age of 45 years or older is associated with increased miscarriage rates and reduced live-birth rates following IUI, whereas no effect was observed for the 40–44 age group.