D-pinitol has been demonstrated to exert insulin-like and anti-inflammatory activities. However, its anti-allergic effect in the Th1/Th2 immune response is poorly understood. Recently, it was shown that T-bet and GATA-3 are master Th1 and Th2 regulatory transcription factors. In this study, we have attempted to determine whether D-pinitol regulates Th1/Th2 cytokine production, T-bet and GATA-3 gene expression in OVA-induced asthma model mice. We also examined to ascertain whether D-pinitol could influence eosinophil peroxidase (EPO) activity. After being sensitized and challenged with ovalbumin (OVA) showed typical asthmatic reactions. These reactions included an increase in the number of eosinophils in bronchoalveolar lavage (BAL) fluid, an increase in inflammatory cell infiltration into the lung tissue around blood vessels and airways, airway luminal narrowing, and the development of airway hyper-responsiveness (AHR). The administration of D-pinitol before the last airway OVA challenge resulted in a significant inhibition of all asthmatic reactions. Accordingly, this study may provide evidence that D-pinitol plays a critical role in the amelioration of the pathogenetic process of asthma in mice. These findings provide new insight into the immunopharmacological role of D-pinitol in terms of its effects in a murine model of asthma, and also broaden current perspectives in our understanding of the immunopharmacological functions of D-pinitol.