Electrothermal-mechanical interaction plays an important role in controlling the performance of electromechanical structures and field-assisted processes. The understanding of electrothermal-mechanical behavior of a material requires the analyses of Joule heating and thermomechanical deformation. In this study, we analyze the current-induced thermal stress in a conducting composite consisting of conducting spherical inclusions at dilute concentration. Assuming that there is no interaction among conducting inclusions, we obtain closed-form solutions of local temperature and thermal stress. The thermal stress created by Joule heating is proportional to the square of electric current density (electric field intensity) and the von-Mises stress reaches the maximum value at the interface between the spherical inclusion and the matrix. Large electric current will likely cause local delamination along the interface.