Injection molding tools are expensive and the fatigue failure during production would result in very costly rework on tool and downtime. Currently mold designs are mostly based on expert experience without a careful stress analysis and the mold set life cycle relies largely on a rough estimates. There are three major causes of mold damage: 1) Thermal stress due to rapid heating and cooling (thermal shock); 2) Mold deflection due to injection pressure imbalance; 3) Clamping force induced stress inside mold blocks. The industry state of the art applies averaged temperature change and peak pressure load on the mold tool and static analysis is performed. Mold temperature history and thermal shock are not considered in the durability analysis. In the developed integrated CAE tool, a transient thermal analysis of the tool is performed in conjunction with the injection molding process simulation. The spatial and temporal variation of temperature, pressure and clamping force is exported from the Moldflow simulation. These histories are converted to appropriate loading curves for an FEA model in Abaqus. A transient FEA simulation is performed in Abaqus for the length of the cycle time with temperature and pressure variation over the entire tool incorporated as loads. Thermo-mechanical stresses are predicted along with contact interactions. These stress histories are used for more accurate fatigue life prediction of the tool. This new methodology would help to avoid the risk of fatigue failure for injection molding tools. Costly tool rework and downtime would be avoided.