Several waste and recycled materials are commonly incorporated into the mix design of asphalt concrete to produce more environmentally friendly construction materials. Among these, Recycled Asphalt Pavement (RAP) is one of the most widely used options, often employed as a partial substitute for natural stone aggregates. However, the inclusion of such recycled materials can adversely affect the mechanical properties, strength, and overall performance of asphalt pavements. In particular, the resistance of asphalt overlays containing high content of RAP against cracking and crack growth tends to decrease. Therefore, it is essential to evaluate the potential effects of RAP incorporation on the cracking resistance of asphalt mixtures. Traffic loading on cracked asphalt pavements and overlays can induce two fundamental crack deformation modes, namely pure mode I (tensile opening) and pure mode II (in-plane shear). In this study, the effect of adding RAP on the fracture toughness of asphalt mixtures in two basic fracture modes (KIc and KIIc) was investigated using Edge-Notched Disc Bend (ENDB) specimens. Fracture toughness tests were performed on Hot Mix Asphalt (HMA) mixtures containing 0%, 25%, and 50% RAP (as replacement of natural aggregates) at three low temperatures: 0 °C, -12 °C, and -24 °C. Based on the results, by increasing the RAP content in asphalt mixtures up to 25%, fracture toughness and fracture energy increased and by adding more RAP up to 50% (high content RAP) fracture toughness and fracture energy decreased compared to the mixtures containing 25% RAP. while, fracture toughness and fracture energy increased compared to the control mixture. Depending on the test temperature and mixture type (HMA with or without RAP content) the KIc and KIIc values were varied from 0.58 to 1.05 MPa.m0.5.