The roots of Zaluzania montagnifolia are traditionally boiled to obtain an aqueous infusion to treat type 2 diabetes mellitus in Oaxaca, México. The objective of this work is to estimate the hypoglycemic effect of the root infusion from Zaluzania montagnifolia in healthy volunteers. One hundred and fifty eight healthy patients (70-100 mg dL^-1 glucose) were subjected to an oral glucose tolerance test (OGTT) but simultaneously, 53 individuals were randomly administered with a standardized root infusion of Z. montagnifolia (4.5 g 250 mL^-1). According to our results, patients treated with the infusion of Z. montagnifolia after the administration of 100 g glucose, showed a statistically significant flattening (p < 0.05) of the OGTT curve compared with the untreated group. The subjects treated with the infusion showed a significant decrease in blood glucose levels (p < 0.05) and this was observed from 30 to 120 min post-treatment. The metabolites dissolved in the infusion were determined by reverse phase-high performance liquid chromatography (RP-HPLC) and gas chromatography-mass spectrometry (GC-MS). Those were principally the diterpenoids ent-kaurenoic acid and grandiflorenic acid. Herein we show a preliminary evidence on the hypoglycemic effect of Z. montagnifolia root extract in humans and the potential use of this plant for the control of type 2 diabetes mellitus after detailed investigation.