Phase formation, crystal structure parameters, dielectric and ferroelectric properties of ceramic solid solutions in the (1-y)[(1-x)(Na0.5Bi0.5)TiO3-x(K0.5Bi0.5)TiO3]-yBiFeO3 system with x = 0.25, y = 0–0.6 has been studied. Pure samples with the pseudocubic perovskite structure were obtained by the solid state reaction method. Addition of BiFeO3 stimulated a monotonous increase in the unit cell volume and in the Curie temperature Tm value. With increasing the BiFeO3 content, nonmonotonous behaviour of the dielectric permittivity, a decrease in the Tph value, a decrease in total electroconductivity and dielectric loss at the room temperature were revealed. © 2017 Taylor & Francis Group, LLC.