Purpose: The purpose of the present study is to explore the influence of body mass index (BMI) on outcomes of in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) techniques in Chinese women with polycystic ovary syndrome (PCOS). Methods: This was a multicenter, prospective, observational study that enrolled 800 subjects with PCOS from nine hospitals in China. Patients were categorized according to BMI categories: underweight, <18.5 kg/m2; normal, 19–23.9 kg/m2; overweight, 24–27.9 kg/m2; and obese, ≥28 kg/m2. Total recombinant follicle-stimulating hormone (rFSH) dose used, estradiol, and progesterone levels on human chorionic gonadotropin (hCG) day; implantation rate; and biochemical, clinical, and ongoing pregnancy rates were compared among BMI categories. Hormone levels (estradiol, follicle-stimulating hormone (FSH), LH, testosterone, and progesterone) were measured using electrochemiluminescence assays. Results: Among the 774 subjects, 27.3 % were overweight and 8.1 % were obese. The rFSH dose used differed significantly among BMI categories (P < 0.001). The implantation rate was lower in obese subjects than that in normal-weight subjects (25.3 vs 45.7 %). Clinical pregnancy rate per transfer differed among BMI categories (P = 0.033), but there was no difference for biochemical (P = 0.327) and ongoing (P = 0.084) pregnancy rates. The miscarriage rate was similar among BMI categories. Conclusions: More than one third of Chinese women with PCOS undergoing IVF/ICSI are overweight or obese. Elevated BMI is associated with reduced clinical pregnancy rate but similar ongoing pregnancy rates, suggesting that BMI has little impact on IVF outcomes. © 2016, Springer Science+Business Media New York.