Abstract. Objective:. To evaluate the effect of morphologic factors on survival rate (SR), pregnancy rate (PR), and implantation rate (IR) of human embryo vitrification following frozen embryo transfer (FET) on day 3 post-ovulation. Methods:. Women undergoing FET (n = 921) with embryos cryopreserved by vitrification between 2012 and 2013 were enrolled in this retrospective cohort study. Results:. Embryos with >9 blastomeres yielded the highest SR of 100%. Lower SR was observed in embryos with 5 to 6 (57.5%) and 4 blastomeres (41.4%). In terms of blastomere symmetry, the SR of embryos with equally sized blastomeres was significantly higher than that of embryos with unequally sized cells (82.5% vs. 64.6%, P