Urotensin II (UII) could increase blood pressure and heart rate via increased central reactive oxygen species (ROS) levels. We reported previously that hydrogen sulfide (H₂S) exerts an antihypertensive effect by suppressing ROS production. The aim of the current study is to further examine the effects of endogenous and exogenous H₂S on UII-induced cardiovascular effects by using an integrated physiology approach. We also use cell culture and molecular biological techniques to explore the inhibitory role of H₂S on UII-induced cardiovascular effects. In this study, we found that cystathionine-β-synthase (CBS), the main H₂S synthesizing enzyme in CNS, was expressed in neuronal cells of the rostral ventrolateral medulla (RVLM) area. Cellular distribution of CBS and urotensin II receptor (UT) in SH-SY5Y cells that are confirmed as glutamatergic were identified by immunofluorescent and Western blots assay. In Sprague–Dawley rats, administration of UII into the RVLM resulted in an increase in mean arterial pressure (MAP), heart rate (HR), ROS production, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, and phosphorylation of p47^phox, extracellular signal-regulated protein kinase (ERK)1/2 and p38MAPK, but not stress-activated protein kinase/Jun N-terminal kinase (SAPK/JNK). These effects of UII were attenuated by application into the RVLM of endogenous (L-cysteine, SAM) or exogenous (NaHS) H₂S. These results were confirmed in SH-SY5Y cells. UII-induced cardiovascular effects were also significantly abolished by pretreatment with microinjection of Tempol, Apocynin, SB203580, or PD98059 into the RVLM. Preincubated SH-SY5Y cells with Apocynin before administration of UII followed by Western blots assay showed that ROS is in the upstream of p38MAPK/ERK1/2. Ga_o activation assay in SH-SY5Y cells suggested that H₂S may exert an inhibitory role on UII-induced cardiovascular effects by inhibiting the activity of Gα_o. These results suggest that both endogenous and exogenous H₂S attenuate UII-induced cardiovascular effects via Gα_o-ROS-p38MAPK/ERK1/2 pathway.