Background: Multi-catheter interstitial brachytherapy (MIB) is one kind of accelerated partial breast irradiation, which applied only to local target breast tissue for patients with breast cancer. The objective of this case report was to report the therapeutic effect of interstitial brachytherapy for treating advanced breast cancer with multiple complications. Case summary: The patient was a 64-year-old woman with diagnosed stage IV breast cancer and multiple complications that included primary liver cancer, post-hepatitis cirrhosis, and hypertension. In October 2016, the patient was treated with chemoembolization for liver cancer, and chemotherapy and targeted molecular therapy in a series for advanced breast cancer at Jilin Province Cancer Hospital before admission to Second Hospital of Jilin University. The tumor in her right breast was about 13.0 cm × 11.0 cm, and the surface was red, swollen, and ulcerated. As the patient was not suitable for surgery and intolerant to further chemotherapy the tumor was treated with interstitial brachytherapy. The brachytherapy was performed once a week, overall three times as doses of 28 Gy in 3 fractions. She was then treated by external radiotherapy with a dose of 50 Gy in 25 fractions. The treatment was ended in December 2016. During the follow-up in January 2017, the original breast mass had necrosed and shrank. No overt bleeding or exudation was found. The patient has survived until now. Conclusions: For this patient with advanced breast cancer and multiple complications, interstitial brachytherapy was an effective treatment.