Diet is a risk factor for gestational diabetes mellitus (GDM). There are few studies on women's diet and glucose tolerance test (GTT) results during pregnancy. The objective of this study was to evaluate the relationship between one's previous diet and the number of abnormal values on the diagnostic GTT in women with GDM. We hypothesized that there would be an inverse relation between antioxidant micronutrient consumption and the number of abnormal GTT values. This cross-sectional study included 60 women diagnosed with GDM (2-h, 75 g-GTT), divided in two groups as follows: 1 abnormal glucose value and 2-3 abnormal values. Shortly after the diagnosis, participants answered a validated food frequency questionnaire to assess their food consumption in the last 6 months. The Mann-Whitney test was used to compare the dietary intake of the participants in the two groups. The participant characteristics were similar. The median intake of total calories, carbohydrates, lipids, and proteins did not differ significantly between groups. Participants with 1 abnormal GTT value had significantly higher intakes of fiber (11.9 vs. 11.0 g/day = 0.049), vitamin D (40.6 vs. 40.4 mcg/day = 0.049), and vitamin C (180.0 vs. 151.0 mg/day = 0.008) than those with 2-3 abnormal values. Our results suggest a possible association between the consumption of fiber and antioxidant micronutrients and the number of abnormal GTT values.