The calcium-substituted barium titanate nanopowders Ba_1–xCa_xTiO₃ (0.2 ≤ x 0.3) have been obtained at room temperature by mechanochemical synthesis. The formation of the perovskite phase was controlled by X-ray diffraction studies at various milling duration. The powders possess the perovskite crystallographic structure directly after milling longer than 10h. The dielectric properties of the ceramics obtained by sintering of the nanopowders were investigated in the temperature range between 300 and 500K. The temperature dependence of permittivity exhibited a single anomaly, which corresponds to the ferroelectric-paraelectric phase transition.