The 90 kDa heat shock protein, Hsp90, is a critical protein in eukaryotes. Mainly cytosolic, this protein is expressed at extraordinary levels and participates in the folding of specific protein substrates. Hsp90 is well preserved and exhibits a chaperone role in the conformational maturation in the cellular stress response, and the nuclear hormone receptors and protein kinases. This protein regulates signal transducing molecules, which include members of the Srckinase family of non-receptor tyrosine kinases, serine/threonine kinases and transcription factors. Hsp90 plays an important role in nitric oxide (NO) production and the activation of all of the isoforms of nitric oxide synthase (NOS). This heat shock protein forms a complex with NOS and facilitates its phosphorylation; thus, NO production from the enzyme is enhanced. The formation of NO improves cardiovascular endothelial functions. Studies have shown that an overexpression of Hsp90 regulates oxygen metabolism in the heart through the regulation of NOS. In particular, the Hsp90-eNOS complex augments the activation of eNOS. Hsp90 associates with eNOS under inactive conditions, and upon the stimulation of endothelial cells with VEGF, estrogen, histamine, shear stress, and statins. Thus, understanding the complete role of Hsp90 signaling in cardiovascular systems will help to develop therapeutic approaches to cure many cardiovascular diseases such as ischemia/reperfusion injuries, atherosclerosis, congestive heart failure etc.