Carbimazole is an antithyroid drug that rarely presents as anaphylactic shock. We hereby report a case of 40-year-old female who was treated with carbimazole for thyrotoxicosis. Patient developed sweating, shortness of breath and altered sensorium after taking single dose of carbimazole. Patient was treated for anaphylactic shock. From this, we want to emphasize that carbimazole can rarely present as anaphylactic shock without any other allergic manifestation. So, patient should be counselled about this rare side effect and early approach to health care facility.