The degradation of strength and stiffness of clayey soil under cyclic loading conditions is of serious concern in geotechnical engineering. This degradation behaviour depends on the initial properties and the loading conditions imposed on the soil. An attempt has been made in this paper to model the response of soil under cyclic loading using the concepts of Critical State Soil Mechanics (CSSM). The Modified Cam Clay model, which was developed based on CSSM, is further modified to predict the response of soil under cyclic loading. The improvements in the predictive capabilities of the proposed modified model, in comparison with an existing cyclic loading model is verified with the published experimental data on natural marine clays. The model is capable of predicting most of the important features of soil behaviour under cyclic loading. This paper deals with the development of the model, its validation with experimental data and comparison with one of the existing models in the literature.