A C/SiC composite panel with defects of known size and of familiar nature was manufactured successfully for nondestructive evaluation. A computed tomography (CT) system was used to detect embedded defects. The results show that CT imaging corresponds well with the designed defects. The defect‐embedded composites undergo relatively greater loss in tensile strength and failure strain than the as‐received samples, although their initial Young's moduli are almost identical. It is also observed that the embedded defects make a significant contribution toward the initiation and accumulation of the damage in the composites, which result eventually in the early failure of the composite.