In this work, we investigated the effect of different Fe₃O₄ (magnetite) contents and temperature on the electrical conductivity, σ, of the polar acrylonitrile butadiene rubber (NBR)/Fe₃O₄ mixture system. We found that the percolation threshold concept holds true for the conductive particle-filled composites where σ undergoes quite a sharp increase when the concentration of magnetite in the mixture exceeds 22%. The temperature dependence of σ was thermally activated below and at the percolation threshold (Pc). Magnetite acted as a reinforcing and conductive filler for NBR. At room temperature and at higher voltages, the electrical current was proportional to the square of voltage (l ∝ V²) for the composites containing 30 phr of magnetite. Moreover, we found that the composites with a magnetite content of 50 phr showed the highest tensile strength and elongation at break, which was due to the formation of optimal physical interlocking and crosslinking. The results of the 100%, 200%, and 300% Young moduli indicate that the moduli are largely correlated with the reinforcement effect of magnetite and the viscosity of the blends from the torque curve.