Barium zirconate, a perovskite oxide has been synthesized by a new procedure using solid state metathesis reaction precursors subjected to sonication. We report the lowest temperature of synthesis with particle size ranging from 20 to 30 nm. The initial stage involves formation of composite hydroxide nanoparticles by the solid state reaction of precursor salts with KOH at ambient temperature followed by sonication. BaZrO3 formation as a consequence of ultrasonicator output power variation and ultrasonic time variation has been studied. Results indicate that the process is convenient, low energy, environmentally benign and having narrow particle size distribution of BaZrO3.