Effects of ultrasonic irradiation on magnesium hydride (MgH₂) suspended in decane were investigated with the purpose of improving its hydrogen desorption process. Firstly, we have found that the presence of MgH₂ improves the sonolysis of decane enhancing the amount of hydrogen evolved during the sonication process. The sonicated-MgH₂ maintains its microstructural properties practically unaltered but a drastic reduction of the particle size of MgH₂ (down to ∼20μm) as well as a high pressure MgH₂ phase are observed. However, no substantial modifications of H-kinetic properties of hydride occur as is determined by thermal desorption measurements. This could be attributed to decomposition of decane during sonication which leads to the formation of carbon compounds that hinder the thermal decomposition of MgH₂.