The inexpensive and green method of synthesis for self-assembled micro/nano structures is an important area of emerging research. Such structures can be chemically tuned with predesigned functional properties. Therefore, they hold very good promise for future applications, e.g., biomedicine, electronic device, solar energy, gas sensing. Here we report for the first time an inexpensive and green method for chemical deposition of magnesium hydroxide (Mg(OH)₂) micro/nano flowers in thin films on commercial soda lime silica glass substrates at room temperature. Under identical conditions, chemically synthesized Mg(OH)₂ powders are also prepared in absence of the soda lime silica glass substrates. The condition that favors the growth of micro/nano flowers in thin films is identified from X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX) data. Finally, the possible growth mechanism of micro/nano flowers in thin films is discussed.