In this study, nanoscale organic rigid-rod compounds were utilized as self-reinforcing composites to enhance the physical properties of an epoxy resin diglycidylether of bisphenol A (DGEBA). First, DGEBA was used to react with an aromatic diisocyanate of methylene diphenyl isocyanate (MDI) to form an urethane linkage. Next, four different organic rigid-rod compounds including 4'-hydroxyphenyl-4-hydroxybenzoate, phenyl 4-hydroxybenzoate, 4,4'-isopropylidenediphenol, and 2-naphthol were incorporated to react individually with the remaining isocyanate groups of the MDI units after the previous step. Finally, the four different rigidrod-modified DGEBA systems were examined using nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, scanning electric microscopy, and mechanical property analyses. Each of the four rigid-rod-reinforced DGEBA systems exhibited greatly improved mechanical properties, e.g., higher tensile strengths and fracture energies.