BACKGROUND To determine the effects of age and the serum anti-Müllerian hormone (AMH) level on in vitro fertilization (IVF) outcomes, especially among young women with low serum AMH levels and older women with high AMH levels. METHODS This study was a cohort study in which a total of 9431 women aged 20-51 years who were undergoing their first IVF cycles were recruited. Ovarian response parameters included the number of retrieved oocytes, the number of 2 pronuclear zygotes (2PN), and the frequency of good-quality embryos (GQE). Pregnancy outcomes included the clinical pregnancy rate (CPR), live birth rate (LBR), miscarriage rate (MR), and cumulative CPR and LBR (CCPR and CLBR). RESULTS Among women under 35 years of age, the ovarian response, CPR, CCPR, LBR and CLBR (p < 0.01) were significantly lower in the low-AMH group than in the average-AMH and high-AMH groups. In women above 35 years of age, the ovarian response, CPR, CCPR and CLBR (p < 0.01) were significantly higher in the average-AMH and low-AMH groups. The LBR in the older high-AMH group was significantly higher (37.45% vs 20.34%, p < 0.01) than that in the older low-AMH group, but there was no difference (37.45% vs 32.46%, p = 0.11) compared with the older average-AMH group. When there was a discrepancy between age and the AMH level, the young low-AMH group showed a poorer ovarian response but a better CPR (58.01% vs 49.44%, p < 0.01) and LBR (48.52% vs 37.45%, p < 0.01) than the older high-AMH group. However, the CCPR (65.37% vs 66.11%, p = 0.75) and CLBR (56.35% vs 52.89%, p = 0.15) between the two groups were comparable. The conservative CLBR in the two discrepancy groups increased until the third embryo transfer and reached a plateau thereafter. CONCLUSIONS Even with a relatively low AMH level, young women still had better pregnancy outcomes following IVF than older women. However, increasing the AMH level improves the cumulative outcomes of the older group to a comparable level through a notable and superior ovarian response.