Asphalt binder is subjected to aging during construction process and service life of asphalt pavement. Aging changes the chemical composition and physical properties of asphalt substantially which can lead to premature distresses on pavement. The changes in properties of the asphalt during the aging process is called aging susceptibility of asphalt. Aging of the asphalt is still a fact in the case of rubber modified binder. The effect of Crumb Rubber Modifier (CRM), interaction parameters, and exchange of the components on the aging behavior of the binder is not fully understood. In this study the effect of CRM modification on short term aging mechanism of asphalt is investigated through distinguishing between the effect of different activities, swelling and dissolution, of CRM on the aging process. Hence, the CRM binder and its extracted liquid phase were aged using Rolling Thin Film Oven. Physical properties of the neat and modified asphalt were measured and compared before and after the aging process and accordingly the aging susceptibility of each sample was calculated. Results show that CRM modification of asphalt significantly affects its aging susceptibility, however, the mechanism of its effect is different depending on the interaction conditions between asphalt and CRM.