Both plan-view and cross-sectional transmission electron microscopy as well as sheet resistance measurement have been applied to study the effects of As+ ion-beam mixing on the epitaxial growth of MoSi2 on (111)Si. Significant improvement in the epitaxial growth of MoSi2 on (111)Si and lower electrical resistivity of the MoSi2 overlayer were found as a result of ion-beam mixing. Island formation was almost completely alleviated in samples implanted under suitable conditions and subsequently annealed up to 1100 °C. The dispersion of impurities near the Mo/Si interface and/or the generation of defects as a result of the ion-beam mixing are thought to be particularly beneficial to the growth of MoSi2 epitaxy on silicon. The ineffectiveness of the ion-beam mixing for the improvement of the silicon surface coverage in some instances is attributed to the more pronounced accumulation of As atoms at the MoSi2/Si interface to increase the interface energy so that island formation becomes energetically more favorable.