Background: Gestational diabetes mellitus (GDM) is associated with adverse outcomes and neonatal complications. Its prevalence has been rapidly increasing over the last decade; it is estimated that one in six pregnant women are diagnosed with GDM. Thus, an effective management approach is necessary for women with GDM. This study investigated the effect of a 12-h comprehensive nutrition care (12h-HNC) on the metabolism and outcomes of pregnant women with GDM and neonatal birth weight and hypoglycemia. Methods: The study included 312 pregnant women with GDM at 24-28 weeks of gestation who were treated in our department from January 2014 to December 2016. They were randomly assigned to receive a 12h-HNC (12h-HNC group, n=158) or traditional one-time nutrition guidance (control group, n=154). Maternal blood glucose levels and weight gain, as well as maternal and neonatal outcomes were evaluated and compared between the groups. Results: Compared to those in the control group, patients in the 12h-HNC group had significantly lower 2-h postprandial glucose levels (P<0.05), lower average weight increase (P<0.05), and better outcomes (P<0.05). Neonatal birth weight and incidence of macrosomia were significantly lower in the 12h-HNC group. The incidence of cesarean section was similar in the two groups (P>0.05). Conclusions: The 12h-HNC enabled better blood glucose and weight increase control, improving both maternal and neonatal outcomes in women with GDM. This comprehensive nutrition intervention may achieve favorable effects in clinical practice.