Thermal cracking is a major concern in mass concrete structures due to excessive temperature differentials between the core and the surface, which can significantly affect durability and long-term performance. This study develops a degree-of-hydration-based thermo-mechanical model to simulate early-age thermal cracking in concrete. Unlike conventional approaches that use the maturity method to account for time and temperature dependence of mechanical properties, the proposed model expresses the degree of hydration as a function of time and temperature using a second-order polynomial Bernhardt function. Mechanical properties such as compressive strength, Young’s modulus, tensile strength, and fracture energy were determined at different ages and correlated with the degree of hydration obtained through nonlinear regression to capture the age-dependent strength development. The model was implemented in COMSOL Multiphysics® by coupling heat transfer and structural mechanics modules, where temperature distributions in a slab measuring 22.8 m × 8.55 m × 1.5 m were computed from the transient heat transfer equation and applied as thermal loads in the structural analysis to evaluate stress and cracking behavior. This study demonstrates how the proposed thermo-mechanical model can be calibrated using experimental data and applied to simulate early-age thermal cracking in real structures, thereby providing a valuable tool for understanding thermal stress development and devising preventive measures in mass concrete applications.