Abstract In this study, nickel nanoparticles (NiNPs) were synthesized and utilized for removing dispersed oil from oilfield-produced water in Sudan. The synthesis process involved using two concentration of hydrazine as a reducing agent and sodium hydroxide as solvent. Physiochemical characterizations, such as X-ray diffraction (XRD) and transmission electron microscopy (TEM), confirmed the successful preparation of NiNPs. The TEM analysis revealed an average particle size ranging from 70 to 90 nm, with a change in morphology from star-shaped to monodispersed spherical particles. The crystal structure analysis confirmed the face-centered-cubic (FCC) configuration of the NiNPs, validating their structural properties. Significantly, the NiNPs demonstrated an impressive capability to remove oil form produced water, achieving a remarkable efficiency of 98% in eliminating dispersed oil from produced water. The oil removal process followed Freundlich isotherms, as evidenced by the high value of the linear regression coefficient. Additionally, the kinetics of the oil removal process conformed well to the pseudo-second-order model, indicating a rapid reaction. This study successfully demonstrated the efficient removal of dispersed oil from produced water using nickel nanoparticles, which interacted physically with the oil particles. These findings highlight the potential of NiNPs as an effective adsorbent for treating oilfield-produced water and mitigating environmental contamination.