Objective. Obesity is a worldwide concern with detrimental health effects including decreased fecundity. However, obesity's impact on in vitro fertilization (IVF) is inconclusive and there is little data concerning poor ovarian responders (POR). This study explored the effects of overweight and obesity on IVF outcomes of POR. Design. We retrospectively evaluated 188 POR undergoing IVF cycles. Methods. Patients were categorized into three groups. Group 1 was normal weight POR (18.5-24.9 kg/m(2), n = 96); Group 2 was overweight POR (25.0-29.9 kg/m(2), n = 52); and Group 3 was obese POR (>= 30.0 kg/m(2), n = 40). Main measured outcomes included IVF outcomes. Results. The oocyte maturity, total gonadotropin dose-duration, and cycle cancellation rates were similar. Obese women had significantly decreased LH levels. LH < 4 mIU/mL had a sensitivity (62%) and a specificity (86%) for IVF failure (AUC: 0.71). Fertilization rates of obese subjects were significantly lower than normal and overweight subjects (p = 0.04). Obese women's clinical pregnancy rates were significantly lower (15%) than normal weight women (33.3%, p = 0.01). Conclusions. Despite similar counts of recruited mature oocytes, obese POR women had decreased fertilization and clinical pregnancy rates. Obesity rather than overweight significantly decreased IVF outcomes in POR.