Although gestational diabetes mellitus (GDM) is associated with an increased risk of maternal and neonatal morbidity, there is no consensus as to the optimal approach of nutritional management in these patients. The present study was designed to assess the effect of the Dietary Approaches to Stop Hypertension (DASH) eating plan on glucose tolerance and lipid profiles of pregnant women with GDM. The present randomised controlled clinical trial was performed among thirty-four women diagnosed with GDM at 24-28 weeks of gestation. Subjects were randomly assigned to consume either the control diet (n 17) or the DASH eating pattern (n 17) for 4 weeks. The control diet was designed to contain 45-55% carbohydrates, 15-20% protein and 25-30% total fat. The macronutrient composition of the DASH diet was similar to the control diet; however, the DASH diet was rich in fruits, vegetables, whole grains and low-fat dairy products, and contained lower amounts of saturated fats, cholesterol and refined grains with a total of 2400 mg Na/d. Fasting blood samples were taken at baseline and after 4 weeks of intervention to measure fasting plasma glucose, glycated Hb (HbA1c) and lipid profiles. Participants underwent a 3 h oral glucose tolerance tests and blood samples were collected at 60, 120 and 180 min to measure plasma glucose levels. Adherence to the DASH eating pattern, compared with the control diet, resulted in improved glucose tolerance such that plasma glucose levels reduced at 60 (21·86 v. 20·45 mmol/l, Pgroup = 0·02), 120 (22·3 v. 0·2 mmol/l, Pgroup = 0·001) and 180 min (21·7 v. 0·22 mmol/l, Pgroup = 0·002) after the glucose load. Decreased HbA1c levels (20·2 v. 0·05 %, Pgroup = 0·001) was also seen in the DASH group compared with the control group. Mean changes for serum total (20·42 v. 0·31 mmol/l, Pgroup = 0·01) and LDL-cholesterol (20·47 v. 0·22 mmol/l, Pgroup = 0·005), TAG (20·17 v. 0·34 mmol/l, Pgroup = 0·01) and total:HDL-cholesterol ratio (20·6 (SD 0·9) v. 0·3 (SD 0·8), Pgroup = 0·008) were significantly different between the two diets. Additionally, consumption of the DASH diet favourably influenced systolic blood pressure (22·6 v. 1·7 mmHg, Pgroup = 0·001). Mean changes of fasting plasma glucose (20·29 v. 0·15 mmol/l, Pgroup = 0·09) were nonsignificant comparing the DASH diet with the control diet. In conclusion, consumption of the DASH eating pattern for 4 weeks among pregnant women with GDM resulted in beneficial effects on glucose tolerance and lipid profiles compared with the control diet.