Cardiovascular diseases are a major global health issue, particularly among menopausal women who experience hormonal fluctuations and increased oxidative stress. Estrogen, a key hormone in females, provides cardioprotection by upregulating cystathionine γ-lyase expression and enhancing hydrogen sulfide production. S-allyl cysteine, found abundantly in aged garlic extract, has been shown to protect against vascular dysfunction through the antioxidative mechanism. Thus, this study aims to investigate the vasodilatory effects of S-allyl cysteine in ovariectomized rats, a model for estrogen deficiency in menopausal women. Female Wistar rats (170–220 g, n = 32) underwent either ovariectomy or sham operations and were given a 21-day recovery period before being sacrificed. The rats’ aortic rings were isolated and suspended in a tissue bath and placed between two tungsten wires, connected to an isometric force transducer. Pre-constriction with phenylephrine (PE, 10−6 M) was followed by S-allyl cysteine incubation and a cumulative dose–response curve using acetylcholine (10−9 to 10−4 M). Statistical analysis was performed using one-way and two-way ANOVA with significance set at p < 0.05. The results indicated a significant increase in aortic relaxation after S-allyl cysteine incubation, which also led to a higher percentage of potassium chloride–induced contraction, suggesting activation of potassium ion channels in the endothelium. This was supported by the observation that dl-propargylglycine, a cystathionine γ-lyase inhibitor, blocked S-allyl cysteine’s vasodilatory effect. The study concludes that S-allyl cysteine modulates vascular function, likely through the cystathionine γ-lyase/hydrogen sulfide signaling pathway. These findings highlight S-allyl cysteine can be a natural supplement that aids in cardioprotection for menopausal women.