The specific heat and thermal diffusivity of Compacted Graphite Iron (CGI) and Spheroidal Graphite Iron (SGI) were measured at temperatures ranging between 373 and 773 K (100 and 500 °C) using differential scanning calorimetry (DSC) and between 298 and 773 K (25 and 500 °C) using the laser flash method, respectively. Specific heat increased with increasing amounts of graphite and pearlite, as well as with Si content. As a recommended value of the specific heat for fully ferritic high-silicon SGI, the following relation was suggested:(Formula presented.) where T is the temperature in Celsius, (Formula presented.) is the mass% of Si, and fg is the area fraction of graphite (%). The thermal diffusivity of cast irons tends to increase with increasing amounts of graphite, and decrease with greater nodularity. It was found that nodularity had a strong influence on thermal diffusivity in the nodularity range of 15–30%.