Synthesis of nickel sulfide (NiS2) impregnated on natural phosphate NP (NP) via a simple co-precipitation ultrasonic-assisted method was reported in this study for elimination of a toxic anionic dye (Indigo carmine), different NiS2-doped NP photocatalysts containing different doping ratios were also tested, characterization techniques were employed to identify NiS2/NP structure (XRD), functional groups (FTIR) and morphology (SEM/EDAX). The characterization results showed successful impregnation of nickel sulfide nanoparticles onto natural phosphate. The material exhibited efficient photocatalytic performance under visible light irradiation for the removal of Indigo Carmin dye reaching 99% at doping ratios of 10 to 1 and 10 to 2. A possible photocatalytic mechanism was proposed to understand the photocatalytic behavior of NiS2/NP. The prepared catalyst appeared to have good adequacy with the kinetic model proposed by Langmuir–Hinshelwood, it also showed excellent reusability.