In this work, the thermal and mechanical interfacial properties of diglycidylether of bisphenol A (DGEBA)/polyurethane modified epoxy (UME-305) blends were investigated. 4,4’-Diaminodiphenyl methane (DDM) was used as a curing agent, and the content of UME-305 in the mixture was 0, 20, 40, 60, 80, and 100 wt%. The cure behaviors of DGEBA/UME-305 blends were studied by DSC. The mechanical interfacial properties were confirmed by critical stress intensity factor (KIC) at 77K and 298K. As a result, the exothermic peaks in DSC results were shifted to higher temperature region as increasing the UME-305 content in the blends. The KIC was also enhanced with increasing the UME-305 content and showing a maximum value at 60 wt.% UME-305.