A method and an apparatus for assessing cardiopulmonary fitness of a user are provided. A method of assessing cardiopulmonary fitness involves measuring a biosignal of a user performing an activity, measuring an exercise intensity of the activity, determining a parameter based on the biosignal and the exercise intensity, estimating a cardiopulmonary fitness index based on the parameter, and assessing the cardiopulmonary fitness of the user based on the cardiopulmonary fitness index.