The electrolysis of water has paved the way towards a clean, efficient and renewable energy source for the future technologies. Therefore, an efficient electrocatalyst is needed. MoS₂ based nonprecious materials are earth-abundant, low cost and promising for the hydrogen evolution reaction. In this study, the effect of sulfur source on the catalytic properties of the MoS₂ nanostructures is investigated. Two different sulfur precursors (i.e., thiourea and L-cysteine) were used for the synthesis of MoS₂ nanostructures. The optimization of the sulfur precursor content was carried out to report the best for the development of the future generation of HER catalysts. The cysteine assisted synthesis results the mixed MoO₃/MoS₂ composite structure which has shown significant effect on the catalytic activity. The low concentrations of cysteine and thiourea have shown excellent catalytic activity and stability in 0.5 M H₂SO₄. TheMoS₂ nanostructures with the cysteine as sulfur precursor have shown low Tafel slope of 81 mV dec-1 and a current density of 30 mA cm-2 is obtained at 0.45 V versus RHE. The superior performance of cysteine-based MoS₂ sample is due to the rapid charge transfer as confirmed by EIS and excellent conductivity as witnessed by low optical band gap. These findings strengthen the understanding of fundamental science of Mo-based catalysts for the development of the future generation of electrocatalysts and energy conversion technologies.