Hydrogen sulfide (H2S) has been reported to have beneficial effects in different pathological conditions. Objectives: the effects of chronic treatment of diabetic rats with GYY4137 (slow releasing H2S donor) or NaHS (fast releasing H2S donor) on the reactivity of the mesenteric bed to vasoactive agonists and the changes in its downstream effectors, ERK1/2 and p38 MAP Kinase have been investigated. In addition, the levels of nitric oxide (NO) and H2S in all groups were measured. Methods: diabetes was induced by a single intraperitoneal (ip) injection of streptozotocin (STZ; 55 mg/kg). Sprague Dawley (SD; n = 10–12/group) rats were randomly divided into six groups: control, STZ-induced diabetic rats, GYY4137-treated control, NaHS-treated control, GYY4137-treated diabetic, and NaHS-treated diabetic. After 28 days of treatment, rats were sacrificed and mesenteric beds were isolated for functional or biochemical studies. The vascular reactivity of the perfused mesenteric bed to norepinephrine, carbachol and sodium nitroprusside were determined by measurement of changes in perfusion pressure. Western blotting was performed to measure the protein expression of ERK1/2, p38, eNOS, and H2S biosynthesizing enzymes cystathionine-β-synthase and cystathionine-γ-lyase. NO and H2S levels were measured in all groups in isolated mesenteric tissues or plasma. Results: diabetes resulted in a significant increase in vasoconstrictor responses to norepinephrine (e.g., 129.6 ± 6.77 mmHg in diabetic vs 89.3 ± 8.48 mmHg in control at 10−7 dose), and carbachol-induced vasodilation was significantly reduced in diabetic mesenteric bed (e.g., 68.9 ± 4.8 mmHg in diabetic vs 90.6 ± 2.2 mmHg in control at 10−7 dose). Chronic treatment of the diabetic rats with GYY4137 resulted in a significant improvement in the response to norepinephrine (e.g., 86.66 ± 8.04 mmHg in GYY4137-treated diabetic vs 129.6 ± 6.77 mmHg in untreated diabetic at 10−7 dose) or carbachol (e.g., 84.90 ± 2.48 mmHg in GYY4137-treated diabetic vs 68.9 ± 4.8 mmHg in untreated diabetic at 10−7 dose). The biochemical studies showed a marked reduction of the protein expression of ERK and p38 and a significant upregulation of the expression of eNOS and H2S synthesizing enzymes after chronic treatment with GYY4137. Plasma levels of NO and H2S were significantly elevated after treatment with GYY4137. However, H2S production in the mesenteric bed showed a marginal elevation in diabetic tissues compared to controls. Conclusion: the results indicate that GYY4137 may be a novel therapeutic tool to prevent diabetes-associated vascular dysfunction.