Objective: Women diagnosed with gestational diabetes mellitus (GDM) remain at high risk of developing type 2 diabetes mellitus in the future. The effectiveness of medical nutrition therapy (MNT) acting on GDM is increasingly becoming noteworthy. Materials and Methods: A retrospective cohort study involving 488 GDM cases was conducted. The prepregnancy weight, weight changes during pregnancy, glucose levels, GDM management, follow-up, and birth outcomes were recorded from 2008 to 2012. Results: Overall, 62.91% of the women received MNT, with an increasing trend from 2008 to 2012 (p < 0.01). The fasting plasma glucose, 2-hour blood glucose, and weight gain at 28 weeks, 32 weeks, and 36 weeks as well as intrapartum were lower in the MNT group than in the non-MNT group. Total weight gain during pregnancy and the rates of adverse events during pregnancy were lower in the MNT group compared to the non-MNT group (all p < 0.05). Moreover, 92.2% of the participants in the MNT group had a normal oral glucose tolerance test result, and the rate of exclusive breastfeeding within 4 months after delivery was 54.4% in the MNT group; both were higher than those of the non-MNT group (66.3%, p < 0.001; 29.3%, p < 0.05). Conclusion: MNT can reduce the incidence of pregnancy complications, increase the exclusive breastfeeding rate, and improve pregnancy outcomes. Copyright (C) 2016, Taiwan Association of Obstetrics & Gynecology. Published by Elsevier Taiwan LLC.