In this work, Ru-doped nickel ferrites (NiFeO) were synthesized by a chemical co-precipitation method. Subsequently, they were annealed at different temperatures. The crystallinity of the samples was evaluated using X-ray diffraction and the morphology of the samples was investigated by scanning electron microscopy and transmission electron microscopy. Dielectric constants and dielectric loss were studied. Ru-doped nickel ferrite samples showed relatively low dielectric constant and loss. Also, the dielectric constant and loss decreased with increasing annealing temperature. Vibrational sample magnetometer analysis shows the hysteresis loop of a soft magnetic nature and the relevant parameters ( and ) have low values that confirmed the nature of the material. Subsequently, gas sensors were fabricated to study hydrogen-sensing properties. The gas sensors showed a response to hydrogen gas at a low temperature (100 °C) with selective response in the presence of NH and CHOH gases. The reasons for electrical, magnetic, and sensing behavior of the samples were discussed in detail.