Objective To examine the association of gestational weight gain and dietary factors with abnormal glucose tolerance (AGT). Methods We conducted a prospective cohort study among 813 Hispanic prenatal care patients in Massachusetts. Gestational weight gain and oral glucose tolerance test results were abstracted from medical records. Dietary intake was assessed using a semi-quantitative food frequency questionnaire. Target weight gain was based on BMI-specific weekly weight gain rates established by the Institute of Medicine (IOM). Results We observed a statistically significant interaction between prepregnancy BMI and weight gain in relation to AGT (P < 0.01). Class II/III (BMI ≥ 35 kg/m²) obese women who had a high rate of weight gain (>0.30 kg/week) or who exceeded target weight were 3–4 times as likely to develop AGT compared to women who gained within IOM ranges (OR = 4.2, 95% CI 1.1–16.0, OR = 3.2 95% CI 1.0–10.5, respectively). Increasing levels of saturated fat and fiber and decreasing levels of energy-dense snack foods and polyunsaturated fat:saturated fat ratio were significantly associated with increased risk of AGT, independent of gestational weight gain. Conclusions Weight gain among class II/III obese women and certain dietary components may represent modifiable risk factors for AGT.