Carbon-Carbon (C-C) composites are becoming increasingly popular in the applications of aerospace and high-speed flight. X-Ray Computed Tomography (XCT) is the preferred technique for nondestructively testing for micro-damage in these materials. However, it is a time consuming and expensive method. Ultrasonic techniques offer a cheaper and more flexible option for testing these materials.The aim of this research is to use the nonlinear resonant ultrasound spectroscopy (NRUS) technique to determine the influence of microscopic material damage in C-C composites on the hysteretic nonlinearity parameter α. This study applies contact and non-contact setups of the NRUS technique to C-C specimens in the pristine and damaged state.Multiple longitudinal and flexural modes of vibration are excited, and the nonlinearity trends are studied for each mode for increasing levels of micro-damage. The efficacy of using NRUS to determine micro-damage from cyclic 3-point bending and high-temperature thermal oxidation are determined.