Recent reports have described cases of metachronous breast metastasis in patients with nasopharyngeal carcinoma. However, no similar cases of synchronous breast metastasis have been reported, and evidence that can be used to support the clinical diagnosis of stage IV nasopharyngeal carcinoma in patients with concurrent breast metastasis remains lacking. Therefore, additional evidence is required to elucidate the clinical characteristics of this condition and aid in the development of optimal management strategies.We report the case of a 46-year-old woman who visited our hospital with a right breast mass as the first symptom. The first pathological biopsy report suggested triple-negative breast invasive carcinoma. Subsequent imaging revealed a nasopharyngeal mass. Further puncture biopsy of the nasopharyngeal mass, molecular pathological Epstein-Barr virus in situ hybridization, and immunohistochemistry confirmed the diagnosis of nasopharyngeal carcinoma with breast metastasis. The patient did not undergo a mastectomy and achieved complete remission after chemotherapy and radiotherapy. She continued to receive oral chemotherapy as maintenance therapy and experienced no recurrence or metastasis during the 6-month follow-up period.This case report suggests that breast specialists should carefully rule out secondary breast cancers when diagnosing and treating breast masses. Furthermore, clinicians should aim to identify the pathological type of the tumor to obtain the most accurate diagnosis and prevent excessive diagnosis and treatment.©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.