Abstract Green tea (GT) and its catechin components have been reported to improve renal dysfunction. Two major components of green tea are epigallocatechin-3-gallate (EGCG) and epigallocatechin (EGC). Proximal tubule cells are major cells in the development of diabetic nephropathy. Hyperglycemia is a primary factor promoting the onset of diabetic nephropathy. Thus, we examined the effects of GT, EGCG, and EGC on high glucose-induced dysfunction in proximal tubule cells. In the present study, high glucose increased the secretion of insulin-like growth factor (IGF)-I, II, and transforming growth factor (TGF) β1 in primary cultured rabbit renal proximal tubule cells. High glucose-induced stimulation of IGFs and TGF β1 secretion was blocked by GT, EGCG, and EGC. In addition, high glucose increased lipid peroxide (LPO) formation and decreased Na+/glucose cotransporter activity as well as cell proliferation in proximal tubule cells, which was blocked by treatment with GT, EGCG, and EGC. In conclusion, GT blocked high glucose-induced dysfunction in proximal tubule cells.