The optical and electrical properties of monolayer MoS₂ and MoS₂ adsorbed with chlorine under uniaxial strain is investigated by using DFT-D2 Grimme approach. As a result of mechanical strain, bandgap of semiconducting monolayer MoS₂ and chlorine adsorbed MoS₂ decreases (in a zig-zag manner), which leads to transition from direct to indirect bandgap material and a semiconductor to metal transition. The red shift mechanism, in which the absorption peak relocated to the lower energy regions of electromagnetic spectrum, was seen in MoS₂ structures subjected to strains of 0.6%, 0.8%, and 1% and also in Cl adsorbed MoS₂ structures subjected to strains of 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, and 1%. Blue shift phenomenon is observed in the remaining strained structures of MoS₂ where the applied values of strain are 0.1%, 0.2% and 0.4%, causing the absorption peaks to shift towards the higher energy values. By application of uniaxial strain on all the structures, absorption boost as well as spread over the entire visible spectrum (380–780 nm) and a very limited absorption is observed in UV band (below 350 nm). There is a good correlation between dielectric constant and refractive index of all adsorbed nanostructures. Additionally, all strained structures are highly efficient across the visible spectrum, making them ideal for optoelectronics and solar harvesting.