Out-of-control reactive oxygen species (ROS) signaling is one of the key events in the pathogenesis of endothelial dysfunction and essential hypertension. We observed that tea polyphenols decreased the production of ROS via regulation of the protein expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in bovine carotid artery endothelial cells (BCAECs). Both green tea polyphenols (GTP) and black tea polyphenols (BTP) down-regulated the expression of NADPH oxidase subunits p22phox and p67phox while up-regulating catalase expression (p < 0.05, respectively). Pre-treatment with GTP or BTP for 24 h significantly decreased the superoxide anion level (p < 0.05) and permeable fluorescence intensities in Ang II-stimulated BCAECs. A decrease in cell permeability was also observed by pre-treatment with diphenylene iodonium chloride (DPI) or vitamin E (p < 0.05, respectively). The result demonstrates that tea polyphenols alleviate angiotensin (Ang) II-induced hyperpermeability mainly by decreasing ROS production. Our results suggest that tea polyphenols regulate ROS-related protein expression and may be beneficial in preventing endothelial cell dysfunction and development of cardiovascular diseases, including hypertension.