SnS₂, as a mid-band-gap semiconductor shows a good potential as an excellent photocatalyst due to its low cost, wide light spectrum response and environment-friendly nature. At the same time, it is also considered as a prospective counter electrode (CE) electrocatlayst for dye-sensitized solar cells (DSSC) due to its good electrocatalytic property. However, to meet the demand of large-scale commercialization of both applications, SnS₂ with superior properties are required. Doping is a facile method to manipulate the optical and chemical properties of semiconductor materials simultaneously. In this work, Ag-doped SnS₂ samples with various doping amounts are prepared via a facile one-step solvothermal route. The product was characterized by XRD, SEM, TEM and UV-VIS spectrometry. The photocatalytic activity of the Ag-doped SnS₂ is studied by degradation of methylene blue dye under solar light irradiation. It’s found increasing Ag dopant concentration can effectively increase solar light adsorption efficiency and accelerated heterogeneous photocatalysis. The optimal concentration of Ag dopant concentration was found to be 5 % with the highest rate constant of 1.8251 hour^-1. It is also found that the DSSC based on 5% Ag-doped SnS₂ CE demonstrates the best performance showing an impressive photovoltaic conversion efficiency of 8.70 % which exceeds the efficiency of Pt-based DSSC (7.88%) by 10.41%, while the DSSC consisting of undoped SnS₂ only exhibits a PCE of 6.47%. Such enhanced efficiency of DSSC is attributed to the effectively improved electrocatalytic activity and mixed conductivity resulted from Ag dopant. Therefore, a proper amount of Ag doping can effectively increase the photocatalytic and electrocatalytic performance of SnS₂ and may pave a new way for large-scale solar energy applications.