<p>In this study, chemical bath deposition (CBD) method was used to prepare FeNiS₂ thin films by employing a fluid blend of iron (II) sulphate, sodium sulphide, nickel nitrate, EDTA and Leishman stain. EDTA and Leishman stain were acted as chelating agents and take part in a vital character in the formation of FeNiS₂ thin films. The characterizations of these thin films were analysed by UV–Visible, FTIR, PL, XRD, SEM, EDAX and AFM. XRD shows that the FeNiS₂thin films have a polycrystalline character along six sided stable phases at room temperature. SEM images exhibit that the delivered films form beautiful appearance which is initiated by the complexing agents. Particle size of the thin films has similar thickness (20.58nm for FeNiS₂ with EDTA, 21.25nm for FeNiS₂ with Leishman and 24.03nm for FeNiS₂, respectively), which was revealed by AFM studies. FeNiS₂ thin films demonstrate the outstanding light interaction properties among enormous optical density in the visible region. Band gap values lie between the ranges of 2.01 and 2.27eV. Hall Effect measurement describes that the FeNiS₂ thin films have n-type behaviour in normal where as they changed to p-type when the addition of complexing agents. From the above conclusions, the fabricated ternary thin films are excellent material used for solar cell applications. PL study indicates the highest photoluminescence intensity in the visible region and it exhibits that all are eco-friendly materials. In such way, the photocatalytic activities of FeNiS₂ thin films were also evaluated by the deterioration of malachite green (MG), crystal violet (CV) and methylene blue (MB) in aqueous solution below sun light illumination. The results indicated that the degradation efficiency after 60&#xa0;min of MB, CV and MG using FeNiS₂ was 89.4%, 85.3% and 82.1%, respectively. The highest degeneration ability was attained by UV irradiation at a shorter wavelength with <i>λ</i> = 254nm using FeNiS₂ thin film as photocatalyst.</p>