Pheochromocytomas are rare tumors in childhood and can mimic many unrelated diseases due to their various presenting symptoms. While hypertension is the most prevalent finding of pheochromocytomas, polyuria and polydipsia are rare and interesting symptoms. In this study we presented a child with unilateral pheochromocytoma, whose first symptoms were polyuria-polydipsia, and hypertension, which were important clues for pheochromocytoma. With the help of clinical and laboratory findings, patient was diagnosed as pheochromocytoma and referred to surgery; with the removal of the tumor the symptoms disappeared. When the family members were screened for multiple endocrine neoplasia (MEN) syndromes, a bilateral pheochromocytoma was diagnosed in his sister and she was also operated on immediately. In this article we emphasized that polyuria-polydipsia may be the first symptoms of pheochromocytoma in children, the importance of blood pressure measurement in initial physical examination and the familial pattern of pheochromocytoma.