Background Radiotherapy (RT) involves the use of ionizing radiation in treating malignancies and benign disorders. However, RT damages target and healthy surrounding tissues in a dose-dependent manner. This effectively reduces patient compliance and quality of life, thereby warranting the prevention of RT-induced adverse effects on skin. Adipose-derived stem cells (ASCs) are used to treat RT-induced damage and platelet-rich plasma (PRP) provides a scaffold that potentiates the effects of ASCs. Thus, the aim of this study was to determine the mechanism employed by ASCs and PRP in protecting against RT-induced adverse effects. Methods We have established an immunodeficient mouse transplantation model using which human hair follicular units were implanted. When the follicular units were macroscopically and microscopically mature and anagenic, we administered localized RT. Subsequently, the mice were randomly divided into 4 groups based on the subcutaneous injection of the following to the irradiated transplantation site: saline, PRP, ASCs, and a combination of ASCs and PRP. Next, we used macroscopic and microscopic analyses to determine the protective effects of the injected solutions on skin and hair follicles. Results Adipose-derived stem cells reduced RT-induced adverse effects, such as impaired wound healing, alopecia, skin atrophy, and fibrosis by suppressing inflammation, dystrophy, degeneration, connective tissue synthesis, and apoptosis and increasing cellular proliferation, differentiation, and signaling. Moreover, these effects were augmented by PRP. Conclusions Thus, co-administering ASCs with PRP in mice prevented RT-induced adverse effects and can be tested for use in clinical practice.