In this study, a fully micromechanical model based on iso-field assumptions is developed for computing the effective coupled thermo-electro-elastic material properties of Macro Fiber Composites (MFCs) in the linear regime. The explicit formulations are derived using the thermo-electro-elastic constitutive equations under the iso-field assumptions and multiple loading conditions. The effects of piezoelectric fiber volume fraction and matrix properties on the effective material constants of MFCs are studied through some examples. In order to validate the accuracy of the present micromechanical formulations, comparisons have been made with other results available in the literature.