Background: The probability of conception occurs before ovulation in natural cycle, thus performing IUI before ovulation should not compromise the pregnancy outcomes. Methods: A retrospective cohort study was conducted at a university hospital during 2007 to 2015. The ovarian stimulation and monitoring were performed as usual. The total of 29 preovulatory IUI, and 221 postovulatory IUI couples were recruited. In postovulatory IUI, 5,000 IU of hCG was injected when dominant follicle reached 17 mm. The IUI was performed 36 to 40 hr afterward. In preovulatory IUI, hCG was injected and IUI was performed simultaneously when the dominant follicle reached the size. Data were compared using independent sample t test and Fisher’s exact test. A p-value of <0.05 was considered statistically significant. Results: The characteristics of both groups were comparable. The cumulative biochemical, clinical, and live birth rates were not different between prevulatory and postovulatory IUI groups (10.3% vs. 16.3%; p=0.407, 10.3% vs. 12.2%; p=0.77 and 10.3% vs. 11.3%; p=0.877, respectively). Conclusion: Performing IUI simultaneously with hCG administration does not compromise pregnancy rate.