SrBi2−xLa x Nb2O9 (x = 0.2, 0.4 and 0.6) Aurivillius materials were prepared by hydrothermal treatment. The powder prepared by this method is highly pure and not agglomerated. The morphology of the samples was characterized by SEM. The dielectric properties of all the compositions were investigated in the temperature range from 25 °C to 500 °C and in the frequency range between 100 Hz and 1 MHz. The dielectric properties at room temperature of the proposed materials can match up with La-doped SrBi2Nb2O9 ceramics prepared via the solid-state reaction method. Partial substitution of bismuth by lanthanum greatly affects the ferroelectric–paraelectric transition temperature, as the ferroelectric–paraelectric phase transition becomes diffuse and the Curie temperature shifts toward lower temperatures typically from 375 to 290 °C. The conductivity results obtained for the samples are explained taking into account the metal-binding energies.