Purpose To assess the association of body mass index (BMI) with serum anti-Mullerian hormone (AMH) and inhibin B (InB) levels among women attending a reproductive medical center. Methods We conducted a cross-sectional study of 8323 women (96.4% were Han race) without polycystic ovary syndrome (PCOS) from the reproductive medical center of Tongji Hospital in Wuhan, China for assisted reproductive technology treatment between January 2016 and May 2018. For each participant, BMI and levels of serum AMH and InB were measured at entry by trained clinical technicians. Multivariate linear regression models were used to quantitatively estimate the associations of continuous and categorical BMI with serum AMH and InB levels. Results Each 1 kg/m(2) increase in BMI was significantly associated with a 1.02% (95% CI: 0.40, 1.65%) and 3.59% (3.11, 4.06%) reduction in AMH and InB levels, respectively. No departure from linearity was observed for either AMH or InB (both P for nonlinear trend >0.05). Overweight and obesity were significantly associated with a 6.01% (0.70, 11.04%) and 18.64% (2.29, 32.26%) reduction in AMH level, and were significantly associated with a 18.80% (15.23, 22.23%) and a 35.44% (25.47, 44.08%) reduction in InB level, respectively. In addition, the association between BMI and AMH level was significantly stronger among women >= 32 years. Conclusions BMI was linearly and inversely associated with AMH and InB levels among women without PCOS. Both overweight and obesity were significantly associated with lower AMH and InB levels.