Tin Sulphide (SnS), one of the main sulfide compounds, has generated a great deal of interest because of its distinctive properties and diverse applications. Pure and Cobalt (Co) doped tin Sulphide (SnS) nanoparticles (NPs) have been synthesized by a facile co-precipitation approach. The synthesized nanoparticles were characterized using various characterization techniques such as X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), Raman, UV-Vis Spectroscopy, Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) studies were used to investigate and confirmed the crystalline, optical, and morphological features of nanoparticles. Under the irradiation of natural sunlight, the synthesised nanoparticles effectively performed as a visible light-activated catalyst for the degradation of Crystal violet (CV) and Bromophenol blue (BP) dyes. A 7% of Co-doped SnS catalyst showed excellent photodegradation efficiency of 95.5% and 93.0% for CV and BP, respectively. Rate constant values of 0.066 and 0.059 min−1 are estimated for CV and BP degradation, respectively. The higher photocatalytic activity might be attributed to Co doping, with the doped Co then playing a substantial role in lowering bandgap and boosting charge carriers, superoxide radical, and hydroxyl radical production, which prevents recombination and thus improves the efficiency and stability of the photocatalyst. Additionally, the toxicity of Vigna radiata seeds that are readily available commercially is evaluated using the treated, untreated dye solution, and control solutions.