Under a creep condition of relatively intense stress, dispersive precipitation of TiC nanoparticles could be promptly brought out within the austenite grain when the iron-nickel-base superalloy was fabricated through the specific production of the ingenious alloy design, applicable electro-slag remelting and high-temperature solution-anneal developed in this study. Both the TiC and coexistent M23C6 precipitates are cubo-octahedral in shape, remaining the cube-to-cube orientation relationship and coherent {111}carbide/γ and {100}carbide/γ interphase interface with the austenite, which bring about the dispersion-strengthening effect so that the time to rupture for the present alloy could be increased by 1.8 times of magnitude relative to the commercial creep-resistant product of the same grade. The improved creep property can be attributed to the mechanism that the nanometer-scale intragranular TiC and submicron intergranular M23C6 can act as pinning points for individual dislocations and grain boundaries, respectively, resulting in the raised Orowan strengthening and suppressed grain boundary sliding. Since the strengthening media found in this study are thermally stable and able to emerge readily prior to the formation of γ’ phase at the temperature range studied, this work suggested an improved grade of heat resistant alloy for applications in a relatively harsh environment that the creep lifetime might be shorter than the incubation period of the common strengthening phase for superalloys.