To best of our knowledge, this is the first reported case of pericardial and pleural effusions combined with ascites, precipitated with severe sunitinib-induced hypothyroidism. A 58-year-old man presented in our emergency department due to dyspnoea and dry cough. Sixteen months earlier, the patient underwent left nephrectomy due to metastatic renal cell adenocarcinoma (RCC), and therapy with sunitinib was initiated postoperatively. Thyroid function was not assessed during the therapy. On admission, all laboratory findings were within normal range. Computed tomography of the chest detected voluminous bilateral pleural effusions and mild pericardial effusion, and echocardiography revealed pericardial effusion. Thoracocentesis was carried out three times, and cytological examination showed no signs of malignant cells. After assessment of the thyroid function, neglected hypothyroidism was registered. Substitution therapy with levothyroxine was initiated, and thyroid function normalised 2 weeks later. Few days after the last thoracocentesis, his condition suddenly got worse. Thoracocentesis was repeated, and microbiological analysis of the exudate came positive for Klebsiella pneumoniae and Streptococcus pneumoniae. Despite the implemented therapeutic measures, his clinical condition progressively deteriorated. The patient died 27 days after the admission, hospital-acquired pneumonia was identified as the cause of death. Our case emphasises the necessity of careful monitoring and management of side-effects in patients who receive sunitinib. Hypothyroidism is a known cause of pleural, pericardial and abdominal effusions, as reported in several case reports. Timely initiation of substitution levothyroxine therapy can decrease unnecessary pauses in the therapy with sunitinib, as well as prevent development of severe symptoms.