Introduction: Thryrotoxic periodic paralysis is a rare complication of thyrotoxicosis presenting as sudden onset of weakness of both lower limbs and sometimes of all four limbs. The complication can occur in a patient with other symptoms of thyrotoxicosis or previously asymptomatic individual. Case report: We report the case of a 40 year old male who presented with sudden onset of weakness of both lower limbs with no sensory or bladder symptoms. On examination, patient had a power of 2/5 in both lower limbs, hypotonia and absent reflexes. Investigations: The serum potassium was 2.2meq/l and thyroid function tests revealed hyperthyroidism. Results: The patient was treated with injection potassium chloride which improved the serum potassium level. Concurrent to the improvement in serum potassium, power of lower limbs also improved. He was then started on methimazole and beta blockers. Discussion: Thyrotoxic periodic paralysis is a rare complication of thyrotoxicosis, more common in Asian males. It can occur in individuals with few or no clinical faetures of thyrotoxicosis. Conclusion: Thyrotoxicosis should be kept in mind while evaluating a case of hypokalemic periodic paralysis as treatment for the same can prevent future recurrences.