Several types of SARS-CoV-2 vaccine have been developed. However, the relationship between SARS-CoV-2 vaccine and radiation therapy (RT) is unclear. Recently, there have been some reports of radiation recall phenomenon (RRP) caused by a SARS-CoV-2 vaccine. We report a case of RRP after administration of the mRNA-1273 SARS-CoV-2 vaccine. A 51-year-old female was diagnosed with breast cancer (cT4N1M0, cStage IIIB) and underwent breast total mastectomy with axillary lymph node dissection after neoadjuvant chemotherapy. After mastectomy, the patient received RT with 50 Gy in 25 fractions. An acute side effect of grade 2 dermatitis according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. occurred after RT. The patient had not started any new systemic medication after RT; however, the patient received the mRNA-1273 SARS-CoV-2 vaccine (Moderna) 1 month after the end of the initial RT. Seven days after vaccination, the patient had a skin reaction with burning sensation and redness. This skin reaction was induced in an area corresponding to the irradiation field of the chest wall. There was no skin reaction in areas other than that described. The reaction was cured within 1 week with topical hydrocortisone. This report is an interesting case report with a RPP after administration of the mRNA-1273 SARS-CoV-2 vaccine.