Experimental evidence has shown significant heat generation in polymer matrix composites subjected to ballistic impact, particularly in resin rich regions where adiabatic conditions prevail. This local matrix heat generation causes subsequent thermal softening, which can have a significant effect on the deformation, progressive damage, and failure behavior under impact loading. In this work, a multiscale modeling approach is used to simulate this experimentally observed phenomenon. The methodology is used to study the impact response of a T700/Epon 862 [0°/60°/–60°] triaxially braided composite. A subcell based approach is used to approximate the heterogeneity of the braid architecture at the highest analysis length scale. The mesoscale repeating unit cell is discretized in-plane into unique mesoscale subcell regions, which are then discretized through-thickness into an approximation of unidirectional plies. The generalized method of cells micromechanics theory is used to bridge the micro (constituent) and macroscales via localization and homogenization. Unified thermo-viscoplastic constitutive equations are used to describe the nonlinear constitutive behavior of the E862 matrix material. Matrix adiabatic heating, due to the conversion of plastic work to heat, is computed via the heat energy equation at the constituent level. A technique based on shifting resin DMA data is used to determine matrix elastic properties at various rates and temperatures. Fiber failure is incorporated into the multiscale framework and is simulated using both the maximum stress criterion and the Curtin progressive fiber damage model. The simulation results indicate that inclusion of the effects of adiabatic heating could have a significant effect on the accurate prediction of the behavior of polymer matrix composite under impact loading.