In this study, Ni1−xZnxFe2O4 (x = 0, 0.25, and 0.5) nanoparticles were successfully synthesized via microwave-assisted combustion method and characterized by XRD, FTIR, and SEM–EDAX. XRD results enunciate that the nanoparticle crystallizes in cubic spinel structure with an average crystallite size (40.2, 37.2, 35.1 nm), and also, the lattice strain, specific surface area, X-ray density were evaluated. The morphology and chemical compositions of Ni, Zn, Fe, and O elements were confirmed by the SEM–EDAX studies. For all the samples, vibrational stretching modes of Mtetra–O site (597 (S1), 593 (S2), 583 (S3) cm−1) and Moctra–O site (416 (S1), 421 (S2), 422 (S3) cm−1) were related to the distribution of the cation Ni2+/Zn2+ and Fe3+ ions among the octahedral and tetrahedral sites. From the UV–Vis–DRS spectra, the optical energy band gap has been estimated to be 1.75–2.01 eV. The dielectric constant and loss were measured by varying the applied frequency (50 Hz to 200 kHz) at room temperature. The electronic polarizability (α) was calculated using Penn analysis, Clausius–Mossotti equation, and energy band gap value. Third-order nonlinear optical parameters such as the nonlinear absorption coefficients (10−5 cm/W), refractive index (10−9 cm2/W) and the third-order nonlinear susceptibilities (10−6 esu) were determined by Z-scan technique. The antibacterial studies were tested against Bacillus cereus, Staphylococcus aureus, Shigalla flexneri and Klebsiella pneumonia bacterial strains. The existing results point out that the synthesized Ni/Zn/Fe2O4 nanoparticles are possible candidates for photonic devices, optical switches, optical limiting and also for pharmaceutical applications. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.