The development of novel synthesis method for the gram scale synthesis of nanostructures is highly important for their practical applications. In this article, we are reporting a unique method for the gram scale preparation of MoO3 nanoplates via facile one step thermal decomposition approach using ammonium molybdate as starting material. The X-ray diffraction and Raman spectral analysis revealed the presence of orthorhombic MoO3. The Fourier transform infra red spectrum confirms the presence of Mo O stretching vibrations in the obtained MoO3 nanoplates. The field emission scanning electron microscope study showed the formation of plate like MoO3 nanostructures. The electrochemical properties of the obtained MoO3 nanoplates are examined by the use of cyclic voltammetry, galvanostatic charge–discharge analysis, and electrochemical impedance spectroscopy. The prepared MoO3 nanoplates exhibited a maximum specific capacitance of about 52 F/g at a scan rate of about 5 mV/s. Electrochemical impedance spectroscopic results such as Nyquist and Bode angle plots suggested the pseudocapacitive nature of the prepared MoO3 nanoplates.