Metaplastic breast cancer is an uncommon and fatal condition. It is described histologically as a tumor having epithelial differentiation into squamous and mesenchymal components, with numerous elements frequently co-existing in the same tumor. This case study sought to provide analgesic treatment in a case with malignant pleural effusion related to breast cancer based on evidence. A 67-year-old female with a known history of metaplastic breast carcinoma came to the tertiary care hospital with complaints of breathlessness which progressed to grade II on the Modified Medical Research Council (mMRC) Dyspnoea Scale, a cough with mucoid expectoration, restlessness, nausea, and reduced appetite for eight days. Diagnostic findings revealed bilateral pleural effusion (left>right). Laboratory investigations revealed that the excess fluid accumulated was transudate in nature, according to the Light's criteria. This case report illustrates the strategy, management, and importance of adherence to pulmonary rehabilitation and painkiller care physiotherapy for patients with metaplastic breast cancer and pleural effusion to achieve the best possible physical and mental health.