The thermal conductivity of unfilled polypropylene foams produced using different foaming processes has previously been demonstrated to be mainly affected by the foam’s bulk density . The influence of adding inorganic particles is now studied, with the thermal conductivity of the mineral-filled PP foams being determined using the Transient Plane Source Method (TPS). To this end, two different fillers were used. The incorporation of high amounts (50 and 70 wt.%) of magnesium hydroxide resulted in considerably higher thermally conductive foamed materials, with interesting thermal anisotropies being observed for the higher expansion ratio foams. On the contrary, adding montmorillonite (MMT) nanoparticles did not considerably alter the thermal conductivity of the foams, their value being mainly affected by the relative density.