A diagnosis apparatus for an internal combustion engine equipped with a cold start emission reduction strategy unit, includes: a temperature measuring unit for detecting a temperature of coolant of the internal combustion engine; a temperature estimating unit for calculating an estimated temperature of the coolant in accordance with a running state of the internal combustion engine; and a cold start emission reduction strategy abnormality judging unit for judging abnormality of the cold start emission reduction strategy unit in accordance with the temperature detected with the coolant temperature measuring means and the estimated temperature.