Objective: The aim of the current study is to assess the presence of such an association between serum progesterone concentrations measured on day of human chorionic gonadotropin (hCG) injection to trigger ovulation and pregnancy outcomes in normal-responding women under ICSI after controlled ovarian hyperstimulation (COH) using the long gonadotropin releasing hormone agonist (GnRHa) protocol. Methods: The study included infertile women who were planned to undergo ICSI for male factor or tubal factor, or for unexplained infertility. All women underwent COH after luteal phase down-regulation using GnRHa. Serum progesterone assay was performed to all included women on the same day before hCG injection. Study outcomes included: positive biochemical pregnancy, positive clinical pregnancy and positive ongoing clinical pregnancy Results: A total of 312 ICSI cycles in 289 women were included in the final analysis. Among the included cycles, the ongoing clinical pregnancy rate was 119/312 (38.1%). Serum progesterone measured on day of hCG injection was a significant predictor of positive biochemical, clinical and ongoing clinical pregnancy as shown the significantly large areas under the curve (AUCs). Binary logistic regression analysis showed that serum progesterone was the only significant independent variable that was associated with a positive ongoing clinical pregnancy. Conclusions: Serum progesterone rise before hCG injection seems to have an adverse effect on pregnancy rates in women undergoing ICSI after COH using the long GnRHa protocol.