There is a need for developing clinically translatable therapy for preventing fetal origins of cardiovascular disease in pregnancy complicated by chronic fetal hypoxia. Evidence shows that sildenafil protects placental perfusion and fetal growth. However, whether beneficial effects of sildenafil transcend onto the fetal heart and circulation in complicated development is unknown. We isolated the direct effects of sildenafil on the fetus using the chick embryo and hypothesised that sildenafil also protects fetal cardiovascular function in hypoxic development. Chick embryos (n = 11 per group) were incubated in normoxia or hypoxia (14% O2) from day 1 and treated with sildenafil (4 mg kg−1 day−1) from day 13 of the 21-day incubation. Hypoxic incubation increased oxidative stress (4-hydroxynonenal, 141.1 ± 17.6% of normoxic control), reduced superoxide dismutase (60.7 ± 6.3%), increased phosphodiesterase type 5 expression (167 ± 13.7%) and decreased nitric oxide bioavailability (54.7 ± 6.1%) in the fetal heart, and promoted peripheral endothelial dysfunction (70.9 ± 5.6% AUC of normoxic control; all P < 0.05). Sildenafil treatment after onset of chronic hypoxia prevented the increase in phosphodiesterase expression (72.5 ± 22.4%), protected against oxidative stress (94.7 ± 6.2%) and normalised nitric oxide bioavailability (115.6 ± 22.3%) in the fetal heart, and restored endothelial function in the peripheral circulation (89.8 ± 2.9%). Sildenafil protects the fetal heart and circulation directly in hypoxic development via mechanisms including decreased oxidative stress and enhanced nitric oxide bioavailability. Sildenafil may be a good translational candidate for human antioxidant therapy to prevent fetal origins of cardiovascular dysfunction in adverse pregnancy.