This study investigated the effect of intravaginal administration of probiotics immediately after oocyte retrieval on vaginal colonization and outcome of the IVF-embryo transfer cycle. One hundred and seventeen women who underwent ovarian stimulation and IVF were randomized immediately after oocyte retrieval into two groups: those who received intravaginal probiotics (study group, n = 50) and those who did not (control group, n = 67). Vaginal colonization with lactobacilli and pregnancy rate were compared between the two groups. No significant between-group differences were observed in patient age, oestrogen and progesterone concentrations on day of human chorionic gonadotrophin administration, number of oocytes retrieved, fertilization rate, number of embryos transferred, or pregnancy rate. The presence of lactobacilli in the vagina during oocyte retrieval or embryo transfer did not improve the pregnancy rate. Furthermore, intravaginal administration of lactobacilli following oocyte retrieval did not affect the prevalence of lactobacilli during embryo transfer, or the pregnancy rate. Intravaginal probiotic supplementation immediately after oocyte retrieval has no effect on vaginal colonization or pregnancy rate in IVF cycles.