We have investigated the voltage-tunable characteristics of the Na(0.5)Bi(0.5)TiO(3)-NaTaO(3) homogeneity region, for which samples were prepared using a conventional solid-state reaction. The highest value of the relative tunability (n(r)) was obtained for the sample with 5 mol% of NaTaO(3), i.e., 47% at 1 MHz and a 70 kV/cm dc bias field. This sample also showed the highest value of the dielectric losses (tan delta) and temperature coefficient of the dielectric constant (tau(epsilon)), i.e., 0.05 and 4478 ppm/K, respectively. As the concentration of NaTaO(3) increased up to 90 mol% n(r), tan delta, and tau(epsilon) gradually decreased toward 22%, 0.0002 and -899 ppm/K, respectively. The dielectric constant of the samples varied in a similar manner between 662 and 130. At microwave frequencies, the dielectric losses of the samples substantially increased due to their relaxor-type nature. The lowest value was obtained for the samples with 90 mol% of NaTaO(3), i.e., 0.002. The tunable characteristics of the samples are related to the ferroelectric and dielectric properties, and it appears that the dielectric tunability of the Na(0.5)Bi(0.5)TiO(3)-NaTaO(3) system originates from its relaxor-type behavior.