Heat removal and “simultaneous” thermal stability are vitally important for the high performance and the long-term reliability of printed electronics. However, such a demand is challenging, because heat-conductive reinforcements also “simultaneously” encourage the thermal expansion/degradation of polymeric materials. To restrict the motion of polymer chains (the key for achieving increased glass transition temperature (T_g) and thus enhancing thermal stability), chemical modifications are often used to intensify the reinforcement/polymer interfacial interactions, but they deteriorate the intrinsic conductivity of the reinforcements. Herein, this deadlock is broken. Moreover, no chemicals are needed. We reveal an inherent superiority of ‘thick’ graphene oxide nanoplatelet (GONP) in enhancing both the thermal conductivity and also the T_g and its associated dimensional and structural thermal stability of epoxy, with a particular emphasis on enabling the thermal conductivity-reinforcing capability of GONPs to make a “positive” contribution to the thermal stability enhancement of epoxy. The strong GONP/epoxy interfacial interaction formed was verified by “local” mechanical properties investigated using nanoindentation. The superiority of the ‘thick’ GONP is based on the specialty of layered-structure and thus can be extended to various GONP-like reinforcements for endowing polymeric materials with high overall thermal properties for printed electronics.