Abstract Study question Can embryo morphology grading be a good parameter to predict the embryo transfer’s outcome when euploid embryos are used? Summary answer Gardner’s grading is a useful predictor of LBR per euploid embryo transferred. Morphologic grading should be used for the embryo selection among euploid blastocysts. What is known already When preimplantation genetic testing for aneuploidies (PGT-A) is not performed, the selection of the embryo(s) to be transferred is based on embryo morphology. In PGT-A cycle, some studies have minimised the importance of embryo morphology, when euploid embryos are present. However, others still consider it as good predictor. Understanding the role of morphology in biopsied euploid embryos may help in optimizing frozen embryo transfer cycles. Study design, size, duration We retrospectively analysed PGT-A frozen embryo transfers with reported outcome, performed in our clinics between 2018 and 2022. The cycles included were divided into two groups based on Gardner’s grading of euploid embryos transferred: “good” embryos (AA, AB, BA and BB; n = 263) versus “poor” embryos (including AC, CA, BC, CB, and CC; n =112). Participants/materials, setting, methods We included in the study only single euploid embryo transfers, double embryos transfers and mosaic embryo transfers excluded. Body mass index (BMI), oocyte age and outcomes (pregnancy and live birth rates) were compared between the two groups. Data was statistically analysed using MedCalc Software, where P < 0.05 was considered as significant. Main results and the role of chance A total of 375 embryo transfer cycles were included in the study. Maternal ages were not significantly different between groups (good vs poor embryos) (37.5 vs 38.2). Similarly, oocyte age (37.7 vs 38.1, respectively), and BMI (22 vs 22.7, respectively) did not differ between good and poor embryos. On the contrary, clinical pregnancy (56.6% vs 40.1%) and live birth rates (27.7% vs 13.4%) were significantly higher when morphologically good grade embryos were transferred (p < 0.05). In fact, both rates were significantly higher after the transfer of blastocysts that exhibited A-grade or B-grade in inner cell mass and/or trophectoderm, as opposed to the transfers of blastocysts that exhibited a C-grade trophectoderm and/or inner cell mass. Limitations, reasons for caution The findings apply to the participating centres and may not represent worldwide trends. Data was analysed retrospectively, but details of the follow-up on PGT pregnancies and babies born were limited. The degree of blastocyst expansion and the day of biopsy were not taken into consideration in this study. Wider implications of the findings The Gardner embryo quality assessment improves the clinics’ ability to prioritize embryos after PGT. Preferential transfer based on morphologic criteria increases the chances of a positive outcome in terms of live birth rates. Trial registration number not applicable