Background. The rate of twin gestations is now about 3% of all pregnancies. The study objective was to investigate the association between twin pregnancy newborn outcomes and maternal weight. Methods. Birth certificate information of 1,342 sets of live-born twin deliveries collected in a regional perinatal data system from a contiguous eight-county area in upstate New York was studied. Results. The obese maternal pre-pregnancy BMI category was correlated with an increased odds ratio of a “Type I” (both a ≥36-week gestation and a ≥2,500-g average twin weight) newborn outcome (adjusted OR 1.92; 95% CI: 1.43, 2.56). For total maternal weight gain, there was an increased odds ratio of having a Type I newborn outcome with >25 kg weight gain (adjusted OR 2.24; 95% CI: 1.51, 3.33). Conclusions. Based on this population-based study, we conclude that both maternal pre-pregnancy BMI and total maternal weight gain are associated with twin newborn outcomes.