Abstract The aim of this prospective randomized study was to determine if the use of intracytoplasmic morphologically selected sperm injection (IMSI) is associated with gender incidence. Couples who underwent IVF-preimplantation genetic screening (PGS) cycles, as a result of advanced maternal age, were randomly allocated into two groups: intracytoplasmic sperm injection (ICSI; n = 80) or intracytoplasmic morphologically selected sperm injection (IMSI; n = 80). The incidences of genders were compared between ICSI-and IMSI-derived embryos. Considering all the biopsied embryos were characterized as normal for sex chromosome, the results showed that IMSI results in a significantly higher incidence of female embryos as compared with ICSI (65.1% versus 54.0%, respectively, P = 0.0277). After analysing only euploid embryos for the eight selected chromosomes, a significantly higher incidence of XX embryos derived from IMSI was also observed compared with ICSI cycles (66.9% versus 52.5%, respectively, P = 0.0322). This result was confirmed by logistic regression, which demonstrated a nearly 2-fold increase in euploid XX embryos derived from spermatozoa selected by high magnification (OR 1.83, 95% CI 1.05-3.35, P = 0.032). A higher proportion of morphologically normal spermatozoa analysed under high magnification seem to carry the X chromosome