Different glomerular diseases are associated with various neoplasms. It seems obvious that Carcinoma of Unknown Primary (CUP) induced nephrotic syndrome is rare. In this regard, the present article introduces a patient suffering from nephrotic syndrome associated with CUP. Patient is a 65-year-old non-smoker male who referred to the clinic for one-month generalized edema. The patient was also complaining from coughing and bulky yellowish sputum with no signs of blood. Patient's chest radiography revealed pulmonary pleural effusion of the left lung, but no other pathological findings were revealed. Patient's cytology report of pleural fluid indicated metastatic carcinoma, and therefore, the patient needed additional examinations so that the origin of metastases (lung, gastrointestinal tract, pancreas, etc.) could be detected. Finally, chemotherapy treatments began when the patient was diagnosed with Carcinoma of Unknown Primary (CUP). With the continuation of chemotherapy treatment and follow-up after more than a year of treatment, the patient is now generally well-off; his nephrotic syndrome has also been in remission parallel to chemotherapy. Significant point in the treatment of this patient is proteinuria, hypercholesterolemia and hyponatremia remission in two stages of chemotherapy. These findings suggest probable para-neoplastic nephrotic syndrome. The treatment of paraneoplastic is the treatment of underlying cause.