Endothelial dysfunction has been shown to be predictive of subsequent cardiovascular events and death. Through a mechanism that is incompletely understood, increased dietary salt intake promotes endothelial dysfunction in healthy, salt-resistant humans. The present study tested the hypothesis that dietary salt-induced TGF-β promoted endothelial dysfunction and salt-dependent changes in blood pressure (BP). Sprague-Dawley rats receiving diets containing 0.3% NaCl (LS) or 8.0% NaCl (HS) were treated with vehicle or SB525334 (SB), a specific inhibitor of TGF-β receptor I/activin receptor-like kinase 5 (ALK5), beginning on day 5. BP was monitored using radio-telemetry in the four groups of rats (LS, LS SB, HS, and HS SB) for up to 14 days. By day 14 of the study, mean daytime systolic blood pressure (SBP) and mean pulse pressure (PP) of the HS group treated with vehicle was greater than the other three groups; mean daytime SBP and PP of the HS SB group did not differ from the LS and LS SB groups. While mean SBP, DBP and MAP did not differ among the groups on the 7th day of the study, endothelium-dependent vasorelaxation was impaired specifically in the HS group; treatment with the ALK5 inhibitor prevented the high dietary salt intake-induced increases in phospho-Smad2 (S465/467) and NADPH oxidase-4 in endothelial lysates and normalized endothelial function. These findings suggest that high salt-induced endothelial dysfunction and the development of salt-dependent increases in BP were related to endothelial TGF-β signaling.