Abstract: The Fe_1−xNi_xVO₄ (where x = 0, 0.05, 0.10, and 0.20) nanoparticles in this work were successfully synthesized via a co-precipitation method. The structural, magnetic and electrochemical properties of the prepared Fe_1−xNi_xVO₄ nanoparticles were studied as a function of Ni content. The experimental results show that the prepared Ni-doped FeVO₄ samples have a triclinic structure. Scanning electron microscopy (SEM) images reveal a decrease in average nanoparticle size with increasing Ni content, leading to an enhancement in both specific surface area and magnetization values. X-ray absorption near edge structure (XANES) analysis confirms the substitution of Ni²⁺ ions into Fe³⁺ sites. The magnetic investigation reveals that Ni-doped FeVO₄ exhibits weak ferromagnetic behavior at room temperature, in contrast to the antiferromagnetic behavior observed in the undoped FeVO₄. Electrochemical studies demonstrate that the Fe_0.95Ni_0.05VO₄ electrode achieves the highest specific capacitance of 334.05 F·g⁻¹ at a current density of 1 A·g⁻¹, which is attributed to its smallest average pore diameter. In addition, the enhanced specific surface of the Fe_0.8Ni_0.2VO₄ electrode is responsible for its outstanding cyclic stability. Overall, our results suggest that the magnetic and electrochemical properties of FeVO₄ nanoparticles could be effectively tuned by varying Ni doping contents.