A recent clinical study demonstrated that haemodialysis with a dialysate containing hydrogen (H ) improves blood pressure control in end-stage kidney disease. Herein, we examined whether H has a salutary effect on hypertension in animal models. We subjected 5/6 nephrectomised rats to inhalation of either H (1.3% H  + 21% O  + 77.7% N ) or control (21% O  + 79% N ) gas mixture for 1 h per day. H significantly suppressed increases in blood pressure after 5/6 nephrectomy. The anti-hypertensive effect of H was also confirmed in rats in a stable hypertensive state 3 weeks after nephrectomy. To examine the detailed effects of H on hypertension, we used an implanted telemetry system to continuously monitor blood pressure. H exerted an anti-hypertensive effect not only during daytime rest, but also during night-time activities. Spectral analysis of blood pressure variability revealed that H improved autonomic imbalance, namely by suppressing the overly active sympathetic nervous system and augmenting parasympathetic nervous system activity; these effects co-occurred with the blood pressure-lowering effect. In conclusion, 1-h daily exposure to H exerts an anti-hypertensive effect in an animal model of hypertension.