1. The aim of the study was to determine if H2S is involved in the development of hypoxia-induced pulmonary hypertension in broilers, a condition frequently observed in a variety of cardiac and pulmonary diseases. 2. Two-week-old broilers were reared under normoxic conditions or exposed to normobaric hypoxia (6 h/day) with tissue levels of H2S adjusted by administering sodium hydrosulfide (NaHS, 10 µmol/kg body weight/day). Mean pulmonary arterial pressure, right ventricular mass, plasma and tissue H2S levels, the expression of cystathionine-β-synthase (CSE) and vascular remodeling were determined at 35 d of age. 3. Exposure to hypoxia-induced pulmonary arterial hypertension was characterized by elevated pulmonary pressure, right ventricular hypertrophy and vascular remodeling. This was accompanied by decreased expression of CSE and decreased concentrations of plasma and tissue H2S. 4. Hypoxia-induced pulmonary hypertension was significantly reduced by administration of NaHS but this protective effect was largely abolished by D, L-propargylglycerine, an inhibitor of CSE. 5. The results indicate that H2S is involved in the development of hypoxia-induced pulmonary hypertension. Supplementing NaHS or H2S could be a strategy for reducing hypoxia-induced hypertension in broilers.