Irradiation causes the impaired proliferation of cells lining mucosal membranes. Epidermal growth factor (EGF) facilitates proliferation of various skin cells; however, the wound healing effects of EGF on radiation-damaged cells is less well known. To evaluate the effects of recombinant human EGF (rhEGF) on the proliferation of cells following irradiation, we tested two types of fibroblast cell lines and one keratinocyte cell line. The viable cell numbers were significantly increased by rhEGF treatment for 24 h immediately after 8 Gy of irradiation. The most effective dose of rhEGF was 10 nM in all cell lines used in this study. The percentage of BrdU-labeled cells was also significantly increased by rhEGF treatment. To evaluate the effects of rhEGF on radiation-induced oral mucosal damage in BALB/c mice, we systematically injected 1 mg/kg/day EGF for three days after 17 Gy of irradiation. Administered rhEGF ameliorated radiation-induced mucosal damage in vivo. rhEGF significantly increased the epithelial cell layer thickness and the proliferation of basal layer cells as detected by Ki-67 staining. Our results suggest that rhEGF can be a therapeutic treatment for radiation-induced wounds by stimulating the proliferation of fibroblasts and keratinocytes following irradiation.