The thermoelectric properties of p-type Mg₂Sn_1-xGe_x thin films grown by molecular beam epitaxy with varying Mg flux rate and the effects of varying Ge fraction to the defects formation were investigated. Higher Mg flux rates tend to be preferable to obtain Mg₂Sn_1-xGe_x epitaxial films with higher p-type carrier mobilities, Seebeck coefficient, and lower thermal conductivity owing to the enhancement of film’s epitaxy at higher Mg flux rate. Vacancy-type point defects are decreasing with increasing Ge fraction which further lowers the total thermal conductivity, were probed from the films whose knowledge is important in further improvement of thermoelectric performance.