In the presence of two-dimensional (2D) nanomaterials, the fracture toughness of polymer-based materials can be improved. This improvement is caused by the occurrence of toughening mechanisms. In the current study, the toughening mechanisms related to the well-dispersed 2D nanofillers, i.e., pull-out, interfacial debonding, and rupture, were modeled based on J-integral concept. In addition, the role of toughening mechanism due to the occurrence of agglomeration phenomenon was accounted for. To verify the presented model, experimental data from the other studies were employed. It was manifested that the results of the presented theoretical model are in good agreement with the empirical data.