A set of thermoviscoplastic nonlinear constitutive relationships (TVP-NCR) is presented. This set is unique and has been developed mainly for application to high-temperature metal matrix composites (HT-MMC) and is applicable to thermal and mechanical properties. Formulation of the TVP-NCR is based at the micromechanics level. The TVP-NCR are of simple form and readily integrated into nonlinear composite structural analysis. Results show that this unique set of TVP-NCR is computationally effective. It provides a direct means for predicting complex materials behavior at all levels of the composite simulation; that is, from the constituent materials, through the several levels of composite mechanics, and up to the global response of complex HT-MMC structural components.