Vitamin D 3 , widely recognized for its key role in maintaining calcium-phosphate homeostasis, also has a multifaceted effect on the regulation of immune, inflammatory and vascular processes, including the maintenance of proper endothelial function. Disruption the endothelial regulation during pregnancy can lead to the development of serious complications, including preeclampsia and fetoplacental insufficiency. The aim of this study was to evaluate the effect of 25(OH)D 3 deficiency on endothelial function parameters in pregnant female rats and to determine its role in the development of endothelial dysfunction in physiological pregnancy and experimental preeclampsia. The experiment was conducted on 35 female Wistar rats divided into three groups: control, vitamin D 3 deficient, and vitamin D 3 deficient with cholecalciferol supplementation. PE was induced by L-NAME administration. The levels of 25(OH)D 3 , endothelial nitric oxide synthase (eNOS), endothelin-1, nitric oxide (NO), malondialdehyde (MDA) and superoxide dismutase (SOD) were measured in serum and tissues. In rats with vitamin D 3 deficiency, there was a decrease in eNOS and NO levels, an increase in endothelin-1, and an increase in markers of oxidative stress. Vitamin D 3 supplementation partially restored these parameters, attenuated oxidative stress, and reduced vasoconstriction. Preeclampsia worsened endothelial dysfunction regardless of vitamin D 3 levels, but the changes were more pronounced in the deficient group. These results confirm the important role of vitamin D 3 in maintaining endothelial function during pregnancy and confirm its potential use in the prevention of vascular and placental complications.