AbstractTo meet the demands of high‐density and miniaturized integrated circuits, electronic packaging materials need to have excellent properties. One approach to enhance the performance is to design novel structures. In this study, two novolac oligomers containing naphthalene Naphthalene novolac oligomer (NPF) and biphenyl Biphenyl novolac oligomer (LPF) were synthesized and then reacted with epichlorohydrin to synthesize novel novolac epoxy resins containing polycyclic aromatic hydrocarbons (NPF‐EP and LPF‐EP). Their chemical structures were characterized by Fourier transform infrared and 1H nuclear magnetic resonance spectra. Tetrahydromethyl‐1,3‐isobenzofurandione (MeTHPA) was used as curing agent to prepare cured NPF‐EP/MeTHPA and LPF‐EP/MeTHPA thermosets. Both NPF‐EP/MeTHPA and LPF‐EP/MeTHPA exhibited better thermal and mechanical properties compared with novolac epoxy resin (PF‐EP/MeTHPA). In particular, NPF‐EP/MeTHPA presented the highest glass transition temperature of 193°C and LPF‐EP/MeTHPA had excellent mechanical properties, with tensile and flexural strengths of 94 and 151 MPa, respectively. Additionally, the cured NPF‐EP/MeTHPA and LPF‐EP/MeTHPA also exhibit a lower dielectric constant and dielectric loss, and low coefficient of thermal expansion compared with cured PF‐EP/MeTHPA. This investigation provides valuable insights for the manufacturing of high‐performance novolac epoxy resins for application in electronic packaging materials.