t—The (1 – x)Nd2(WO4)3–xSiO2 composites where the silicon oxide mole fraction is x ≤ 0.5 were manufactured by the solid-phase method. The phase compositions of the composites and their thermodynamic stability were verified by X-ray powder diffraction and thermogravimetry, respectively, in combination with differential scanning calorimetry (DSC). The morphology of the composites was studied by scanning electron microscopy (SEM) combined with energy-dispersive X-ray analysis. The electrical conductivity of the composites measured by electrochemical impedance was studied as functions of temperature, oxygen vapor pressure, and the amount of silicon oxide (the dispersed additive). The sums of ion transference numbers were studied as a function of temperature by the EMF method; the ionic character of conduction in the composites was found. The composite-conductivity effect was found to occur in the studied system: additions of 30 mol % nanosized silica to neodymium tungstate increased the ionic conductivity by more than two orders of magnitude.