Adequate weight gain during pregnancy is one of the factors for its proper course. Excessive weight gain during this period of a woman’s life is associated with adverse pregnancy outcomes. In this study, we determine the impact of excessive gestational weight gain on pregnancy outcomes. The study is based on the results of a Polish national survey performed between 2011 and 2017 on a group of 10,319 women and 6930 children. Excessive weight gain during pregnancy was associated with higher birthweight and higher prevalence and risk of birthweight over 4500 g (OR 6.92; 95% CI 3.10–15.42), cesarean section/assisted delivery (OR 2.71; 95% CI 1.63–4.49), pregnancy induced hypertension (OR 5.85; 95% CI 3.24–10.57), hospitalization during pregnancy (OR 1.85; 95% CI 1.12–3.04), and the Apgar score in the first minute of neonate’s life in the range of 0–7 (OR 2.65; 95% CI 1.36–5.2). We did not observe the significant difference in premature rupture of membranes and labor inductions. Our study indicates that excessive gestational weight gain is associated with higher risk for adverse pregnancy outcomes.