This work describes the green synthetic process for magnesium sulfide nanoparticles (MgS NPs) using an extract from Hordeum vulgare leaves. An examination of the MgS NPs was performed utilizing X-ray diffraction (XRD), UV-visible spectroscopy, and scanning electron microscopy (SEM) techniques. The MgS NPs generated were spherical and had a high level of purity. They had a band gap of 2.0 eV, a uniform distribution, and an average crystal size of 14 nm. The MgS nanoparticles synthesized exhibited several geometrical morphologies, including spherical, rod-shaped, and bean-shaped structures. The nanoparticles exhibited an average size of 5 nm, with a band gap of precisely 4.85 eV. The efficacy of MgS NPs on Brassica nigra and Trigonella foenum-graecum for seed priming, germination rate and time, root length, and shoot length has been assessed using different doses. Optimal germination occurs at concentrations of 15mg/100ml and 20mg/100ml, while germination is impeded when the concentration surpasses 30mg/100ml. MgS NPs exhibit a diminutive size and elevated reactivity, which allows them to augment the water absorption and nutrient control capacities of seeds. Consequently, this promotes the germination process and plant growth by decreasing the average duration of germination. Seeds of Brassica nigra and Trigonella foenum-graecum that had been subjected to treatment with MgS NPs had enhanced average root and shoot lengths, as well as accelerated germination. The results of this study suggest various promising opportunities for investigating the application of environmentally friendly nanotechnology to improve agricultural practices.