Phellinus baumii is a mushroom used as a folk medicine for a variety of human diseases in several Asian countries. Recently we have reported for the first time about the antidiabetic effect of the crude exopolysaccharides (EPS) produced from submerged mycelial culture of P. baumii in streptozotocin (STZ)-induced diabetic rats. The diabetic rats study revealed that orally administrated P. baumii EPS lowered the blood glucose levels and stimulated insulin excretion in diabetic rats, and consequently restored the functions of pancreas, liver, and kidney, suggesting that the EPS might be useful for the management of human diabetes mellitus. We undertook proteomic analyses for plasma, pancreas, liver, and kidney of the rats to search for novel biomarkers for monitoring diabetes before and after EPS treatments. In this article, we describe the production of EPS in submerged culture of P. baumii and studies of their hypoglycemic activity. We also explore the issue of proteomic analyses for mining biomarkers of diabetes.