Abstract: Ensuring thermodynamic self-consistency in constitutive equations is a critical requirement for simulating material creep behavior, as it pertains not only to the theoretical rigor of the model but also directly impacts its reliability in engineering applications. Leveraging the laws of energy conservation and non-negative entropy production, this study develops a thermodynamically consistent creep constitutive model that incorporates damage evolution. The model decomposes the material’s total free energy into two components: one linked to creep deformation and damage, which describes the influence of micro-defect evolution on deformation hardening and strength degradation; and another associated with elastic-plastic deformation, reflecting the transient mechanical response under loading. This framework establishes explicit relationships among stress, strain, and damage variables during creep and enables accurate prediction of material lifespan through damage-controlled evolution equations. Validation against high-temperature creep data for P92 alloy and 1Cr10NiMoW2VNbN alloy demonstrates that the model effectively captures the evolution of creep strain and precisely predicts creep life across varying stress levels. These results underscore the applicability and robustness of the model for lifespan assessment in high-temperature structural materials.