Introduction: Gestational diabetes (GD) is one of the most common medical complications of pregnancy, associated with increased incidence of pre-eclampsia, macrosomia, and cesarean delivery. Insulin therapy is the cornerstone treatment in those individuals with inadequate glycemic control by diet alone. The burden of insulin treatment includes the need for multiple injections, intensive blood glucose monitoring, risk of hypoglycemia, and emotional distress. Alternatives to insulin treatment have been studied in the past but there is limited previous experience with acarbose. Objective: To compare acarbose to insulin therapy and evaluate the proportion of subjects requiring rescue therapy with insulin due to inadequate glycemic control; as a secondary objective, pregnancy outcomes were assessed. Materials and Methods: Pregnant patients diagnosed with GD who failed glycemic control on dietetic treatment, were randomized to receive standard insulin therapy or acarbose. If the oral drug was not tolerated or glycemic goals were not met, standard insulin therapy was initiated. Results: A total of 104 patients were randomized (acarbose n = 40). Two patients in the acarbose group and six in the insulin group withdrew their consent before any study intervention due to personal preferences. In the acarbose group, 27/38 subjects (71%) achieved and maintained glycemic targets until delivery, while 11/38 (29%) received rescue insulin therapy and discontinued the study drug. No differences were found in birth weight, gestational age at birth, or Apgar score. Three patients in the acarbose and five in the insulin group presented perinatal complications. Conclusion: In this study, acarbose was found to be a safe and effective alternative to insulin therapy. Insulin therapy and its burden were avoided in over 70% of the GD patients failing nutritional therapy. Studies with a larger sample size and long-term follow-up are needed.