Ceramic matrix composites (CMC) are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems due to their low density, high thermal conductivity, and excellent mechanical properties. Specifically, silicon carbide-fiber reinforced silicon carbide (SiC/SiC) is a very creep resistant material with high temperature capability, that is being developed for such uses. Due to their brittle nature, one factor currently necessary for the implementation of these materials is the ability to accurately monitor and predict damage evolution. Current nondestructive evaluation methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. CMC is a multifunctional material in which the damage is coupled with the material’s electrical resistance, providing the possibility of real-time information about the damage state through monitoring of resistance. In this thesis, an electrical resistance-based nondestructive evaluation method is developed to detect the damages in SiC/SiC at room and high temperature. For undamaged samples, it was found that the resistivity is affected by composite constituent content and fiber architecture. Room temperature monotonic tensile tests of SiC/SiC composites were performed, coupled with modal acoustic emission and resistance monitoring. The results show excellent electrical sensitivity to mechanical damage. Room temperature experiments were able to correlate matrix cracking with resistance increases. Also, creep tests at 1315°C, coupled with resistance monitoring, were conducted. The high temperature creep tests also showed significant electrical resistance changes, although it is more difficult to isolate the specific causes since damage progression in creep is much more complicated. These experiments demonstrate that electrical resistance can be used both for in situ damage monitoring and also as a post-damage inspection method. A multi-physical model was also developed to explain and interpret the results as well as link the resistance change to the mechanical damage such as fiber breaks and matrix cracks. The predictions agree reasonably well with the experimental results.