The objective of this investigation was to assess the antihyperglycemic effects of an extract of decaffeinated green coffee beans (EDGCB). Despite the potential properties attributed to this compound, little is known about its action in vivo. In rats, EDGCB significantly decreased postprandial blood glucose levels when administered with each of the 4 carbohydrate types (sucrose, maltose, glucose, and soluble starch). An optimum effect was observed when EDGCB was administered at the beginning of the carbohydrate challenge. In the clinical trial, plasma glucose levels were significantly reduced by administering doses of 100 and 300 mg EDGCB after ingestion of 200 g carbohydrate, particularly in subjects with a high glycemic response. No significant differences were observed in plasma insulin profiles, however, over the course of the experiment.