OBJECTIVE : Does a woman's ethnicity affect her fresh and frozen embryo transfer outcomes differently? METHODS : A retrospective cohort study of the first fresh and first frozen embryo transfer per woman carried out at a single tertiary level fertility unit between 2010 and 2016 using data retrieved from an electronic database. Biochemical pregnancy, biochemical pregnancy loss, clinical pregnancy, miscarriage and live birth rates per embryo transfer were compared between 5876 white Caucasian, 1071 South Asian and 114 Black Afro-Caribbean women undergoing their first fresh embryo transfer and for 1418 Caucasian, 273 South Asian and 31 Afro-Caribbean women undergoing their first frozen embryo transfer. Logistic regression was used to adjust for age, number of oocytes retrieved, and number and stage of embryos transferred. RESULTS : South Asian (26% versus 32%, adjusted OR 0.622, 95% CI 0.533 to 0.725) and Black Afro-Caribbean women (21% versus 32%, adjusted OR 0.528, 95% CI 0.332 to 0.839) had a lower live birth rate per fresh embryo transfer compared with white Caucasian women. In contrast, the live birth rates per frozen embryo transfer were not significantly different between South Asian and Caucasian women (26% versus 28%, adjusted OR 0.890, 95% CI 0.661 to 1.200) and between Afro-Caribbean and Caucasian women (29% versus 28%, adjusted OR 0.983, 95% CI 0.447 to 2.162). CONCLUSIONS : South Asian and Black Afro-Caribbean women have a significantly lower live birth rate than white Caucasian women after fresh embryo transfer, but their frozen embryo transfer live birth rates are not significantly different.