The objective was to determine the effect of metformin on the concentrations of resistin and other markers of insulin resistance or inflammation (C-reactive protein, cytokines, body weight, HbA1c, among others) in minors with glucose intolerance. Patients aged 4 to 17 years with glucose intolerance were studied. They were randomized to receive 850 mg of either metformin or placebo twice daily for 12 weeks, during which all followed an iso-caloric diet and an exercise program. High sensitivity C-reactive protein, TNF-alpha, IL-6, IL1-beta, resistin, leptin, adiponectin, glucose, insulin, HbA1c, lipid profile and transaminases were measured at the beginning and at the end of the period. Fifty-two patients were included, 11.9±2.6 years old; 28 (12 males/16 females) received metformin and 24 placebo (11 males/13 females). Baseline characteristics were similar between groups (except for body mass index, which in the metformin group was slightly higher). Percentage weight loss was greater in the metformin group (−5.86% vs 2.75%, P<.05). At study end, there were statistically significant differences in resistin concentrations, even after adjusting for confounding variables (F=7.714; P<.006). Also, metformin was associated with a significant decrease in HOMA-IR index (P=.032) and HbA1c levels (P=.001), but no change was observed in the concentration of other markers of inflammation. Metformin resulted in significant reductions of plasma resistin levels in minors with glucose intolerance. This change is independent of its effects on body weight. In contrast, metformin did not alter the concentration of inflammatory markers.