Breastfeeding is known to have a positive impact on both maternal and neonatal health. It has been demonstrated that mothers with gestational diabetes mellitus (GDM) have lower breastfeeding rates compared to mothers without diabetes but it is less clear how breastfeeding success compares between mothers who have diet controlled (A1) GDM compared to those who require medication for glucose control (A2). This is a secondary analysis of a prospective cohort study of 600 women with GDM funded by the American Diabetes Association. Eligible women were diagnosed with GDM by either a 1-hour glucose challenge test value > 200 mg/dl or by the Carpenter-Coustan criteria using the 3-hour 100 gram glucose tolerance test and enrolled during their delivery hospitalization. Baseline demographic, antepartum and detailed neonatal information were recorded in addition to mode of infant feeding at hospital discharge and 3 months postpartum. Breastfeeding was classified as any or exclusive breastfeeding. Women with A1 GDM were compared to women with A2 GDM using Fischer’s exact test. Of the 600 women consented to participate 301 had A1 and 299 had A2 GDM. Mothers with A1 and A2 GDM had similar rates of any breastfeeding at hospital discharge (242 (80.4%) vs 228 (76.4%); p=0.24); however, exclusive breastfeeding rates at hospital discharge were lower in A2 GDM mothers compared to A1 GDM (28.9% vs. 38.2%; p=0.02). Similar findings were noted at three months; no difference in any breastfeeding (84.3% vs 87.5%; p=0.28), but a difference in exclusive breastfeeding (13.9% vs 26.6%; p=< 0.001). Among women who were exclusively breastfeeding at hospital discharge, exclusive breastfeeding continuation at 3 months postpartum was decreased in women with A2 compared to A1 GDM (53.3% vs 74.8%; p=0.004). Mothers with A2 GDM had decreased rates of both initiating and continuing exclusive breastfeeding postpartum compared to mothers with A1 GDM. Further investigation is needed to determine additional barriers that mothers with A2 GDM may face when attempting to exclusively breastfeed.