A simple and efficient strategy to modify epoxy dynamic polymer networks (DPNs) is presented. The introduction of the flexible epoxidized form of naturally occurring soybean oil (ESO) into epoxy DPNs markedly improves their mechanical properties, stress relaxation rate and malleability. Specifically, at 7.5 wt% ESO loading, the elongation at break of the as-produced epoxy-ESO DPNs was increased from 10% to 108%, the stress relaxation time decreased from 6100 s to 2570 s at 120 °C, and the reprocessing temperature was reduced by 26 °C, which is advantageous for expanding the scope of applications of these materials, especially for reducing the energy consumption during reprocessing. At this composition, the epoxy-ESO DPNs also showed excellent self-healing, welding and chemical degradation properties. This work provides a novel pathway to fabricate epoxy-based DPNs with high performance in an energy-conserving manner.