Thyrotoxic hypokalemic periodic paralysis (THPP) is a rare hyperthyroidism-related endocrine disorder seen predominantly in men of Asian origin. The main characteristics of the disease are hyperthyroidism, hypokalemia, muscle weakness and acute paralysis. We describe a 24-year old male patient with thyrotoxic hypokalemic periodic paralysis presented with symmetrical motor weakness in lower extremities. When he woke up in the morning, he noticed the weakness in both arms and legs, also he recognized that he can not walk. According to his history, similar symptoms occurred and resolved a few months ago. Although hypokalemic periodic paralysis is a rare disorder, clinicians should have a high index of suspicion for patients presenting with walking abnormalities, flaccid paralysis and hypokalemia. Early recognition of thyrotoxicosis and treatment by the emergency physician is necessary to prevent THPP related complications.