Summary: Our objective was to determine the effect of inducing an accessory corpus luteum (CL) using gonadotropinreleasing hormone (GnRH) or human chorionic gonadotropin (hCG) on the day of embryo transfer (ET) on pregnancy per ET (P/ET), calving/ET, and pregnancy loss in recipient dairy heifers and lactating cows receiving in vitro-produced (IVP) embryos. Recipients were randomly assigned to receive GnRH, hCG, or no treatment (control) immediately before ET on days 6 to 9 of the estrous cycle. Parity and embryo characteristics were factors that affected the fertility outcomes of GnRH and hCG treatments on the day of ET. Overall, treatments did not have a major impact on P/ET or calving/ET and had no effect on pregnancy loss; however, the high P/ET results in the present study may have reduced any beneficial impact of accessory CL formation.