In this paper, both standard and constrained thermomechanical fatigue (TMF) tests were conducted on a high silicon ductile cast iron (DCI). The standard TMF tests were conducted with independent control of mechanical strain, out-of-phase (OP) and in-phase (IP) strain, and temperature in the range from 300 to 800°C. The constrained TMF tests were conducted with various constraint ratios of 100%, 70%, 60% and 50% at the temperature ranges of 160 to 600°C and 160 to 700°C. Based on a material model as calibrated with low-cycle fatigue (LCF) data of DCI, finite element analyses (FEA) of the above TMF tests were carried out with Abaqus. A damage mechanism-based lifetime model was integrated into a C++ API code to post-process the Abaqus output results. Simulation predictions show good agreement with experiments for stress-strain responses and lifetime under different TMF conditions.