This study investigates the physical characteristics of un- and Mn-doped SnS nanoparticles (NPs) synthesized through a co-precipitation method. The undoped SnS is referred to as Mn 0, while Mn 1, Mn 2, and Mn 3 samples are obtained by incorporating 1, 3, and 6 mL of Mn-dopant solution, respectively. Elemental analysis is done by means of energy-dispersive X-ray spectroscopy (EDX), confirming successful Mn incorporation into the SnS lattice. X-ray diffraction (XRD) studies validate the formation of the SnS phase with a preferred orientation at the (040) plane for all samples. The crystallite size (D) of SnS NPs initially increases and then decreases after Mn-doping, confirmed by transmission electron microscopy (TEM) images. Field emission scanning electron microscopy (FESEM) images exhibit grain-shaped morphology with sizes ranging from 23 to 36 nm for all samples. The reduction in bandgap energy (Eg) upon Mn-doping is attributed to variations in grain size and the formation of impurity levels within the SnS band gap. Mott-Schottky analysis showed p-type conductivity for all samples. The semiconductor parameters of SnS, such as the acceptor concentration (NA) and the density of states (NV), improved after Mn-doping. Current-voltage (I-V) curves revealed that the conductivity and mobility of SnS after Mn-doping initially declined for Mn 1 and Mn 2 samples and then improved for the Mn 3 sample. Electrochemical impedance spectroscopy (EIS) results align with the I-V findings. Consequently, it can be concluded that Mn-doping leads to enhancements in optoelectronic properties of SnS.