In this work, we report superparamagnetic nanocrystalline NiFe2O4 material was synthesized by using a simple, novel thermal decomposition approach in a controlled manner. However, using ethylene glycol as solvent yielded well dispersed NiFe2O4 nanoparticles. The synthesized NiFe2O4 nanoparticles are characterized by various analytical measurements, and their corresponding optical, morphological, structural, magnetic, and thermal properties of these nanoparticles have been investigated. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicated that the synthesized nanoparticles are in single nanocrystalline cubic phase and the particles are in spherical shaped with an average diameter of 12.3 + 0.69 nm. The magnetic properties of the nanoparticles are studied by vibrating sample magnetometer (VSM) and the results exhibited superparamagnetism at room temperature with the magnetic saturation of (Ms) 36.8 emu/g. Furthermore, the antibacterial activities of the synthesized material was investigated on two Gram-negative (Escherichia coli, Acinetobacter baumannii) and one Gram-positive (Staphylococcus aureus) bacterial strains. The biological results indicated that the synthesized magnetic nanocrystalline NiFe2O4 sample has shown an excellent antibacterial activity against all examined bacteria. In addition, the electrocatalytic performances of the fabricated electrode materials were investigated by cyclic voltammetry.