Abstract Background The aim of this study was to examine the effect of thyroid-stimulating hormone (TSH) levels on intrauterine insemination (IUI) outcomes among euthyroid women. Methods A retrospective cohort study was conducted. A total of 302 women who started their first IUI cycle in our fertility center were included in this study. The patients were categorized into two groups based on their preconception TSH values: 0.38–2.49 mIU/Land 2.50–4.99 mIU/L. The clinical pregnancy rate was the main outcome parameter. As secondary parameters, we evaluated the differences in spontaneous abortion rate, live-birth delivery rate, and perinatal outcomes according to the preconception TSH threshold (