Luteal phase deficiency as a result of multifollicular development which produces supraphysiological progesterone and estradiol levels and benefit of luteal phase support have been proven in assisted reproductive technique (ART) treatment. But, there were some controversial results in intrauterine insemination (IUI) cycles whether luteal phase support (LPS) with progesterone have an impact on pregnancy outcome. To assess the efficacy of vaginal progesterone gel in the gonadotropin-induced IUI cycles, this retrospective data analysis compared the luteal phase support and control group in terms of clinical pregnancy (CPR) and live birth rates (LBR). In subgroup analysis, multifollicular and monofollicular growth were analyzed separately. In total, after exclusion criteria, 380 IUI cycles were analyzed, cycles were grouped as LPS(+) and LPS(-) with 190 and 190 cycles, respectively. CPR and LBR were comparable between groups (11.6% vs. 10.5, p = .74 and 8.9% vs. 8.4%, p = .75 respectively). Although multifollicular growth demonstrated higher pregnancy outcomes than monofollicular growth, intermediate follicles (14-16 mm) had a positive impact on pregnancy outcome in monofollicular growth like multifollicular subgroup. We found no difference in CPR and LBR according to the luteal phase vaginal progesterone gel. Nevertheless, multifollicular cycles and also monofollicular growth cycles with two and more intermediate follicles may have benefit LPS in gonadotropin-induced IUI cycles.