Magnesium hydroxide submicroplatelets were synthesized from laterite leaching solutions by using two methods, namely, precipitation and hydrothermal methods. X-ray diffraction results coupled with Fourier transform infrared spectrometry indicated that all the samples were well-crystallized Mg(OH)(2) with a hexagonal structure. Scanning electron microscope images showed that nanosized Mg(OH)(2) synthesized by the hydrothermal method have transformed into regular, scattered, and well-defined hexagonal platelets. Thermogravimetry-differential scanning calorimetry analysis demonstrated that Mg(OH)(2) submicroplatelets synthesized by the hydrothermal method became more stable.