A 62-year-old postmenopausal woman was diagnosed with breast cancer in her left breast and received modified radical mastectomy (molecular type: hormone-receptor-positive human epidermal growth factor receptor-2 negative). After that, she received postoperative chemotherapy and radiotherapy. After 2 years of tamoxifen adjuvant endocrine treatment, the patient inccurred recurrence with metastasis. PET-CT scanning showed metastasis in the left thoracic wall, the sixth left rib, and the right lower lobe of the lung. Multiple lymph node metastases were observed throughout the body. Palbociclib in combination with an aromatase inhibitor (AI) was used, but the metastatic lesion at the sixth left rib increased than before. Subsequently, the lesion shrunk and the clinical symptoms were relieved, which was considered as a pseudoprogression. Herein, we reported a pseudoprogression in the breast cancer patient after treatment with palbociclib plus AI.