OBJECTIVE Are blastocysts derived from in-vitro-matured metaphase I (MI) oocytes less likely to produce usable embryos for transfer compared with those derived from in-vivo-matured oocytes in cycles undergoing preimplantation genetic testing (PGT)? METHODS The primary outcome was usable blastocyst rate, which was compared between blastocysts derived from in-vitro-matured MI oocytes after ovarian stimulation and from in-vivo-matured oocytes. Logistic regression analysis using generalized estimating equations was used to control for confounders in the analysis of factors that may influence the chance of a blastocyst being usable and in the comparison of embryological outcomes. Student's t-test, Mann-Whitney U test, chi-squared tests or Fisher's exact tests were used to compare clinical and pregnancy outcomes. RESULTS A total of 1810 injected metaphase II (MII) oocytes from 154 PGT cycles involving 154 couples were included in this study. A total of 1577 MII oocytes were in-vivo-matured and 233 were in-vitro-matured MI oocytes. The usable blastocyst rate was similar between the in-vitro-matured MI oocyte group and the in-vivo-matured oocyte group (adjusted RR 0.97, 95% CI 0.40 to 2.34). Three live births were achieved using usable blastocysts derived from in-vitro-matured MI oocytes. CONCLUSIONS If in-vitro-matured MI oocytes can be fertilized and develop into blastocysts, their ability to provide usable embryos for transfer is similar compared with those developed from in-vivo-matured oocytes. These blastocysts could be considered valuable for women with few viable embryos in assisted reproductive technology cycles.