Despite many well-recognized benefits, administration of ionizing radiation before surgical resection of malignancies is associated with a high risk of wound-healing complications. Most animal models investigating techniques to improve wound healing use a superficial wound. The goal of this study was to develop a novel model of radiation-impaired healing using a deep excisional wound, which is closer to the clinical situation. In the first part of this study, female Lewis rats were exposed to 0, 12, 15, or 18 Gy single-fraction radiation to the buttocks. Three weeks later, deep wounds were created by excision of the gluteus maximus muscle. Irradiated wounds had a lower rate of healing of the surgically created defect than unirradiated wounds (p<0.001), but there was no significant difference between the different doses of radiation. Impaired healing was still evident at 12 weeks. The second part of this study investigated the ability of porcine small-intestinal submucosa (SIS) to improve healing in this animal model. At 6 weeks, wounds implanted with SIS showed improved healing at all doses of radiation compared with unimplanted irradiated wounds. However, higher doses of radiation were still associated with a lower rate of healing. SIS induced a cellular response that was not evident in defects that did not receive SIS, suggesting that SIS has the potential to stimulate repair. This reproducible model of radiation-impaired wound healing closely resembles the clinical setting. The results indicate that this model can be used to investigate new biomaterials as possible therapeutic agents to enhance wound healing.